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<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
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<title>Detailed Semantics</title>
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<div class="section">
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
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<a name="boost_optional.detailed_semantics"></a><a class="link" href="detailed_semantics.html" title="Detailed Semantics">Detailed Semantics</a>
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</h2></div></div></div>
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<p>
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Because <code class="computeroutput"><span class="identifier">T</span></code> might be of reference
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type, in the sequel, those entries whose semantic depends on <code class="computeroutput"><span class="identifier">T</span></code> being of reference type or not will be
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distinguished using the following convention:
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</p>
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<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
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<li class="listitem">
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If the entry reads: <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code><span class="emphasis"><em>(not
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a ref)</em></span><code class="computeroutput"><span class="special">></span></code>, the
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description corresponds only to the case where <code class="computeroutput"><span class="identifier">T</span></code>
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is not of reference type.
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</li>
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<li class="listitem">
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If the entry reads: <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span></code>, the description corresponds only
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to the case where <code class="computeroutput"><span class="identifier">T</span></code> is
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of reference type.
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</li>
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<li class="listitem">
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If the entry reads: <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code>, the description is the same for both
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cases.
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</li>
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</ul></div>
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<div class="note"><table border="0" summary="Note">
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<tr>
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<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../doc/src/images/note.png"></td>
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<th align="left">Note</th>
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</tr>
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<tr><td align="left" valign="top"><p>
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The following section contains various <code class="computeroutput"><span class="identifier">assert</span><span class="special">()</span></code> which are used only to show the postconditions
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as sample code. It is not implied that the type <code class="computeroutput"><span class="identifier">T</span></code>
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must support each particular expression but that if the expression is supported,
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the implied condition holds.
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</p></td></tr>
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</table></div>
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<p>
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<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
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</p>
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<h4>
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<a name="boost_optional.detailed_semantics.h0"></a>
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<span class="phrase"><a name="boost_optional.detailed_semantics.optional_class_member_functions"></a></span><a class="link" href="detailed_semantics.html#boost_optional.detailed_semantics.optional_class_member_functions">optional
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class member functions</a>
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</h4>
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<p>
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<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
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</p>
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<a name="reference_optional_constructor"></a><div class="blockquote"><blockquote class="blockquote"><p>
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<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">()</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
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</p></blockquote></div>
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<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
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<li class="listitem">
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<span class="bold"><strong>Effect:</strong></span> Default-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
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</li>
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<li class="listitem">
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<span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">uninitialized</span>.
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</li>
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<li class="listitem">
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<span class="bold"><strong>Notes:</strong></span> T's default constructor <span class="underline">is not</span> called.
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</li>
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<li class="listitem">
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<span class="bold"><strong>Example:</strong></span>
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<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
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<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">def</span> <span class="special">)</span> <span class="special">;</span>
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</pre>
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</li>
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</ul></div>
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<p>
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<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
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</p>
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<a name="reference_optional_constructor_none_t"></a><div class="blockquote"><blockquote class="blockquote"><p>
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<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
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</p></blockquote></div>
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<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
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<li class="listitem">
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<span class="bold"><strong>Effect:</strong></span> Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>
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uninitialized.
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</li>
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<li class="listitem">
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<span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">uninitialized</span>.
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</li>
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<li class="listitem">
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<span class="bold"><strong>Notes:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>'s
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default constructor <span class="underline">is not</span> called.
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The expression <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">none</span></code> denotes an instance of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">none_t</span></code> that can be used as the parameter.
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</li>
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<li class="listitem">
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<span class="bold"><strong>Example:</strong></span>
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<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">none</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
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<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">n</span><span class="special">(</span><span class="identifier">none</span><span class="special">)</span> <span class="special">;</span>
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<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">n</span> <span class="special">)</span> <span class="special">;</span>
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</pre>
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</li>
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</ul></div>
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<p>
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<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
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</p>
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<a name="reference_optional_constructor_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
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<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code>
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</p></blockquote></div>
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<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
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<li class="listitem">
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<span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_copy_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>
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is <code class="computeroutput"><span class="keyword">true</span></code>.
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</li>
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<li class="listitem">
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<span class="bold"><strong>Effect:</strong></span> Directly-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
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</li>
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<li class="listitem">
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<span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>
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and its value is a <span class="emphasis"><em>copy</em></span> of <code class="computeroutput"><span class="identifier">v</span></code>.
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</li>
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<li class="listitem">
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<span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span>
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<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span></code>
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throws.
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</li>
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<li class="listitem">
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<span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span>
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<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span></code>
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is called.
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</li>
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<li class="listitem">
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<span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
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be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span>
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<span class="keyword">const</span><span class="special">&</span>
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<span class="special">);</span></code> in that case, this constructor
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has no effect.
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</li>
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<li class="listitem">
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<span class="bold"><strong>Example:</strong></span>
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<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
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<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
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<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
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</pre>
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</li>
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</ul></div>
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<p>
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<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
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</p>
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<div class="blockquote"><blockquote class="blockquote"><p>
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<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">ref</span> <span class="special">)</span></code>
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</p></blockquote></div>
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<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
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<li class="listitem">
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<span class="bold"><strong>Effect:</strong></span> Directly-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
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</li>
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<li class="listitem">
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<span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>
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and its value is an instance of an internal type wrapping the reference
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<code class="computeroutput"><span class="identifier">ref</span></code>.
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</li>
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<li class="listitem">
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<span class="bold"><strong>Throws:</strong></span> Nothing.
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</li>
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<li class="listitem">
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<span class="bold"><strong>Example:</strong></span>
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<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
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<span class="identifier">T</span><span class="special">&</span> <span class="identifier">vref</span> <span class="special">=</span> <span class="identifier">v</span> <span class="special">;</span>
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<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">vref</span><span class="special">);</span>
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<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
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<span class="special">++</span> <span class="identifier">v</span> <span class="special">;</span> <span class="comment">// mutate referee</span>
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<span class="identifier">assert</span> <span class="special">(*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span><span class="special">);</span>
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</pre>
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</li>
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</ul></div>
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<p>
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<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
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</p>
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<a name="reference_optional_constructor_move_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
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<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span>
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<span class="identifier">v</span> <span class="special">)</span></code>
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</p></blockquote></div>
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<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
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<li class="listitem">
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<span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>
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is <code class="computeroutput"><span class="keyword">true</span></code>.
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</li>
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<li class="listitem">
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<span class="bold"><strong>Effect:</strong></span> Directly-Move-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
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</li>
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<li class="listitem">
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<span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>
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and its value is move-constructed from <code class="computeroutput"><span class="identifier">v</span></code>.
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</li>
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<li class="listitem">
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<span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span>
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<span class="identifier">T</span><span class="special">&&</span>
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<span class="special">)</span></code> throws.
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</li>
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<li class="listitem">
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<span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span>
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<span class="identifier">T</span><span class="special">&&</span>
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<span class="special">)</span></code> is called.
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</li>
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<li class="listitem">
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<span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
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be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">);</span></code>
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in that case, the state of <code class="computeroutput"><span class="identifier">v</span></code>
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is determined by exception safety guarantees for <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span><span class="special">&&)</span></code>.
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</li>
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<li class="listitem">
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<span class="bold"><strong>Example:</strong></span>
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<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v1</span><span class="special">,</span> <span class="identifier">v2</span><span class="special">;</span>
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<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">v1</span><span class="special">));</span>
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<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v2</span> <span class="special">)</span> <span class="special">;</span>
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</pre>
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</li>
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</ul></div>
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<p>
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<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
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</p>
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<div class="blockquote"><blockquote class="blockquote"><p>
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<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="identifier">ref</span> <span class="special">)</span> <span class="special">=</span> <span class="keyword">delete</span></code>
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</p></blockquote></div>
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<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
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<span class="bold"><strong>Notes:</strong></span> This constructor is deleted
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</li></ul></div>
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<p>
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<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
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</p>
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<a name="reference_optional_constructor_bool_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
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<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span></code>
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</p></blockquote></div>
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<div class="blockquote"><blockquote class="blockquote"><p>
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<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="special">::</span><span class="identifier">optional</span><span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> <span class="identifier">T</span><span class="special">&</span>
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<span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span></code>
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</p></blockquote></div>
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<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
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If condition is true, same as:
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</li></ul></div>
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<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code>
|
|
</p></blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="special">::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&</span>
|
|
<span class="identifier">v</span> <span class="special">)</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
|
|
otherwise, same as:
|
|
</li></ul></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">()</span></code>
|
|
</p></blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="special">::</span><span class="identifier">optional</span><span class="special">()</span></code>
|
|
</p></blockquote></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_optional_constructor_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">optional</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">);</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_copy_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>
|
|
is <code class="computeroutput"><span class="keyword">true</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Effect:</strong></span> Copy-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Postconditions:</strong></span> If rhs is initialized,
|
|
<code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is initialized and its value is a <span class="emphasis"><em>copy</em></span> of the value
|
|
of <code class="computeroutput"><span class="identifier">rhs</span></code>; else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is
|
|
uninitialized.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span>
|
|
<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span></code>
|
|
throws.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> If rhs is initialized, <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span></code>
|
|
is called.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
|
|
be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span>
|
|
<span class="keyword">const</span><span class="special">&</span>
|
|
<span class="special">);</span></code> in that case, this constructor
|
|
has no effect.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">uninit</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span>
|
|
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">uninit</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span>
|
|
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">init</span><span class="special">(</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">);</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
|
|
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">init</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">init</span> <span class="special">)</span> <span class="special">;</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">optional</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">);</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Effect:</strong></span> Copy-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
|
|
is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is initialized and its value is another reference to the same object referenced
|
|
by <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>;
|
|
else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is uninitialized.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
|
|
is initialized, both <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
and <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>
|
|
will reefer to the same object (they alias).
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">uninit</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span>
|
|
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">uninit</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span>
|
|
|
|
<span class="identifier">T</span> <span class="identifier">v</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">ref</span> <span class="special">=</span> <span class="identifier">v</span> <span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">init</span><span class="special">(</span><span class="identifier">ref</span><span class="special">);</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
|
|
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">init</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
|
|
|
|
<span class="identifier">v</span> <span class="special">=</span> <span class="number">3</span> <span class="special">;</span>
|
|
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init2</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_optional_move_constructor_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">optional</span><span class="special">&&</span> <span class="identifier">rhs</span>
|
|
<span class="special">)</span> <span class="keyword">noexcept</span><span class="special">(</span></code><span class="emphasis"><em>see below</em></span><code class="computeroutput"><span class="special">);</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>
|
|
is <code class="computeroutput"><span class="keyword">true</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Effect:</strong></span> Move-constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
|
|
is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is initialized and its value is move constructed from <code class="computeroutput"><span class="identifier">rhs</span></code>;
|
|
else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is uninitialized.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span>
|
|
<span class="identifier">T</span><span class="special">&&</span>
|
|
<span class="special">)</span></code> throws.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
|
|
is initialized, <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span>
|
|
<span class="special">&&</span> <span class="special">)</span></code>
|
|
is called. The expression inside <code class="computeroutput"><span class="keyword">noexcept</span></code>
|
|
is equivalent to <code class="computeroutput"><span class="identifier">is_nothrow_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
|
|
be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">);</span></code>
|
|
in that case, <code class="computeroutput"><span class="identifier">rhs</span></code> remains
|
|
initialized and the value of <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> is determined by exception safety
|
|
of <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span><span class="special">&&)</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">uninit</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span>
|
|
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">uninit</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span>
|
|
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">init</span><span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">uniqye_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="keyword">new</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">))</span> <span class="special">);</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
|
|
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">init</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">init</span> <span class="special">);</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="keyword">nullptr</span> <span class="special">);</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">init2</span> <span class="special">);</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">optional</span> <span class="special">&&</span>
|
|
<span class="identifier">rhs</span> <span class="special">);</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Effect:</strong></span> Move-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
|
|
is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is initialized and its value is another reference to the same object referenced
|
|
by <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>;
|
|
else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is uninitialized.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
|
|
is initialized, both <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
and <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>
|
|
will reefer to the same object (they alias).
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&></span> <span class="identifier">uninit</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span>
|
|
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">uninit</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span>
|
|
|
|
<span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">v</span><span class="special">(</span><span class="keyword">new</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">))</span> <span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&></span> <span class="identifier">init</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
|
|
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&></span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">init</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
|
|
|
|
<span class="special">*</span><span class="identifier">v</span> <span class="special">=</span> <span class="number">3</span> <span class="special">;</span>
|
|
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init2</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_optional_constructor_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
|
|
<span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">);</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Effect:</strong></span> Copy-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
|
|
is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is initialized and its value is a <span class="emphasis"><em>copy</em></span> of the value
|
|
of rhs converted to type <code class="computeroutput"><span class="identifier">T</span></code>;
|
|
else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is uninitialized.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span>
|
|
<span class="identifier">U</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span></code>
|
|
throws.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span>
|
|
<span class="identifier">U</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span></code>
|
|
is called if <code class="computeroutput"><span class="identifier">rhs</span></code> is initialized,
|
|
which requires a valid conversion from <code class="computeroutput"><span class="identifier">U</span></code>
|
|
to <code class="computeroutput"><span class="identifier">T</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
|
|
be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span>
|
|
<span class="keyword">const</span><span class="special">&</span>
|
|
<span class="special">);</span></code> in that case, this constructor
|
|
has no effect.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">x</span><span class="special">(</span><span class="number">123.4</span><span class="special">);</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">x</span> <span class="special">==</span> <span class="number">123.4</span> <span class="special">)</span> <span class="special">;</span>
|
|
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">y</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span><span class="special">(</span> <span class="special">*</span><span class="identifier">y</span> <span class="special">==</span> <span class="number">123</span> <span class="special">)</span> <span class="special">;</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_optional_move_constructor_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
|
|
<span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">>&&</span>
|
|
<span class="identifier">rhs</span> <span class="special">);</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Effect:</strong></span> Move-constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
|
|
is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is initialized and its value is move constructed from <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>; else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is uninitialized.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span>
|
|
<span class="identifier">U</span><span class="special">&&</span>
|
|
<span class="special">)</span></code> throws.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span>
|
|
<span class="identifier">U</span><span class="special">&&</span>
|
|
<span class="special">)</span></code> is called if <code class="computeroutput"><span class="identifier">rhs</span></code>
|
|
is initialized, which requires a valid conversion from <code class="computeroutput"><span class="identifier">U</span></code>
|
|
to <code class="computeroutput"><span class="identifier">T</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
|
|
be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span> <span class="special">);</span></code>
|
|
in that case, <code class="computeroutput"><span class="identifier">rhs</span></code> remains
|
|
initialized and the value of <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> is determined by exception safety
|
|
guarantee of <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span> <span class="special">)</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">x</span><span class="special">(</span><span class="number">123.4</span><span class="special">);</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">x</span> <span class="special">==</span> <span class="number">123.4</span> <span class="special">)</span> <span class="special">;</span>
|
|
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">y</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">x</span><span class="special">))</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span><span class="special">(</span> <span class="special">*</span><span class="identifier">y</span> <span class="special">==</span> <span class="number">123</span> <span class="special">)</span> <span class="special">;</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_optional_constructor_factory"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">InPlaceFactory</span><span class="special">></span>
|
|
<span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
|
|
<span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">InPlaceFactory</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">f</span> <span class="special">);</span></code>
|
|
</p></blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">TypedInPlaceFactory</span><span class="special">></span>
|
|
<span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
|
|
<span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">TypedInPlaceFactory</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">f</span> <span class="special">);</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Effect:</strong></span> Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>
|
|
with a value of <code class="computeroutput"><span class="identifier">T</span></code> obtained
|
|
from the factory.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>
|
|
and its value is <span class="emphasis"><em>directly given</em></span> from the factory
|
|
<code class="computeroutput"><span class="identifier">f</span></code> (i.e., the value <span class="underline">is not copied</span>).
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Whatever the <code class="computeroutput"><span class="identifier">T</span></code>
|
|
constructor called by the factory throws.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> See <a class="link" href="tutorial/in_place_factories.html" title="In-Place Factories">In-Place
|
|
Factories</a>
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
|
|
be thrown during the call to the <code class="computeroutput"><span class="identifier">T</span></code>
|
|
constructor used by the factory; in that case, this constructor has no
|
|
effect.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">C</span> <span class="special">{</span> <span class="identifier">C</span> <span class="special">(</span> <span class="keyword">char</span><span class="special">,</span> <span class="keyword">double</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="special">)</span> <span class="special">;</span> <span class="special">}</span> <span class="special">;</span>
|
|
|
|
<span class="identifier">C</span> <span class="identifier">v</span><span class="special">(</span><span class="char">'A'</span><span class="special">,</span><span class="number">123.4</span><span class="special">,</span><span class="string">"hello"</span><span class="special">);</span>
|
|
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">C</span><span class="special">></span> <span class="identifier">x</span><span class="special">(</span> <span class="identifier">in_place</span> <span class="special">(</span><span class="char">'A'</span><span class="special">,</span> <span class="number">123.4</span><span class="special">,</span> <span class="string">"hello"</span><span class="special">)</span> <span class="special">);</span> <span class="comment">// InPlaceFactory used</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">C</span><span class="special">></span> <span class="identifier">y</span><span class="special">(</span> <span class="identifier">in_place</span><span class="special"><</span><span class="identifier">C</span><span class="special">>(</span><span class="char">'A'</span><span class="special">,</span> <span class="number">123.4</span><span class="special">,</span> <span class="string">"hello"</span><span class="special">)</span> <span class="special">);</span> <span class="comment">// TypedInPlaceFactory used</span>
|
|
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">x</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">y</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_optional_operator_equal_none_t"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Effect:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized destroys its contained
|
|
value.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is uninitialized.
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_optional_operator_equal_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span>
|
|
<span class="keyword">const</span><span class="special">&</span>
|
|
<span class="identifier">rhs</span> <span class="special">)</span>
|
|
<span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Effect:</strong></span> Assigns the value <code class="computeroutput"><span class="identifier">rhs</span></code> to an <code class="computeroutput"><span class="identifier">optional</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized and its value is a
|
|
<span class="emphasis"><em>copy</em></span> of <code class="computeroutput"><span class="identifier">rhs</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span></code> or <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&)</span></code> throws.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> was initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s
|
|
assignment operator is used, otherwise, its copy-constructor is used.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Exception Safety:</strong></span> In the event of an exception,
|
|
the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is unchanged and its value unspecified
|
|
as far as <code class="computeroutput"><span class="identifier">optional</span></code> is concerned
|
|
(it is up to <code class="computeroutput"><span class="identifier">T</span></code>'s <code class="computeroutput"><span class="keyword">operator</span><span class="special">=()</span></code>).
|
|
If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is initially uninitialized and <code class="computeroutput"><span class="identifier">T</span></code>'s
|
|
<span class="emphasis"><em>copy constructor</em></span> fails, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is left properly uninitialized.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span> <span class="special">;</span>
|
|
|
|
<span class="identifier">T</span> <span class="identifier">y</span><span class="special">;</span>
|
|
<span class="identifier">def</span> <span class="special">=</span> <span class="identifier">y</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">y</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>&</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&</span>
|
|
<span class="identifier">rhs</span> <span class="special">)</span>
|
|
<span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Effect:</strong></span> (Re)binds the wrapped reference.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized and it references the
|
|
same object referenced by <code class="computeroutput"><span class="identifier">rhs</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> was initialized, it is <span class="emphasis"><em>rebound</em></span>
|
|
to the new object. See <a class="link" href="tutorial/rebinding_semantics_for_assignment_of_optional_references.html" title="Rebinding semantics for assignment of optional references">here</a>
|
|
for details on this behavior.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span>
|
|
<span class="keyword">int</span> <span class="identifier">b</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span>
|
|
<span class="identifier">T</span><span class="special">&</span> <span class="identifier">ra</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span>
|
|
<span class="identifier">T</span><span class="special">&</span> <span class="identifier">rb</span> <span class="special">=</span> <span class="identifier">b</span> <span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">def</span> <span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">ra</span><span class="special">)</span> <span class="special">;</span>
|
|
|
|
<span class="identifier">def</span> <span class="special">=</span> <span class="identifier">rb</span> <span class="special">;</span> <span class="comment">// binds 'def' to 'b' through 'rb'</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">b</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="special">*</span><span class="identifier">def</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span> <span class="comment">// changes the value of 'b' to a copy of the value of 'a'</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">b</span> <span class="special">==</span> <span class="identifier">a</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="keyword">int</span> <span class="identifier">c</span> <span class="special">=</span> <span class="number">3</span><span class="special">;</span>
|
|
<span class="keyword">int</span><span class="special">&</span> <span class="identifier">rc</span> <span class="special">=</span> <span class="identifier">c</span> <span class="special">;</span>
|
|
<span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">rc</span> <span class="special">;</span> <span class="comment">// REBINDS to 'c' through 'rc'</span>
|
|
<span class="identifier">c</span> <span class="special">=</span> <span class="number">4</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="number">4</span> <span class="special">)</span> <span class="special">;</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_optional_operator_move_equal_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="identifier">rhs</span>
|
|
<span class="special">)</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Effect:</strong></span> Moves the value <code class="computeroutput"><span class="identifier">rhs</span></code> to an <code class="computeroutput"><span class="identifier">optional</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized and its value is moved
|
|
from <code class="computeroutput"><span class="identifier">rhs</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code>
|
|
or <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span>
|
|
<span class="special">&&)</span></code> throws.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> was initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s
|
|
move-assignment operator is used, otherwise, its move-constructor is used.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Exception Safety:</strong></span> In the event of an exception,
|
|
the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is unchanged and its value unspecified
|
|
as far as <code class="computeroutput"><span class="identifier">optional</span></code> is concerned
|
|
(it is up to <code class="computeroutput"><span class="identifier">T</span></code>'s <code class="computeroutput"><span class="keyword">operator</span><span class="special">=()</span></code>).
|
|
If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is initially uninitialized and <code class="computeroutput"><span class="identifier">T</span></code>'s
|
|
<span class="emphasis"><em>move constructor</em></span> fails, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is left properly uninitialized.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span> <span class="special">;</span>
|
|
|
|
<span class="identifier">T</span> <span class="identifier">y1</span><span class="special">,</span> <span class="identifier">y2</span><span class="special">,</span> <span class="identifier">yR</span><span class="special">;</span>
|
|
<span class="identifier">def</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">y1</span><span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">yR</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">y2</span><span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">yR</span> <span class="special">)</span> <span class="special">;</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>&</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span>
|
|
<span class="identifier">rhs</span> <span class="special">)</span>
|
|
<span class="special">=</span> <span class="keyword">delete</span><span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> This assignment operator is deleted.
|
|
</li></ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_optional_operator_equal_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span>
|
|
<span class="keyword">const</span><span class="special">&</span>
|
|
<span class="identifier">rhs</span> <span class="special">)</span>
|
|
<span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Effect:</strong></span> Assigns another <code class="computeroutput"><span class="identifier">optional</span></code> to an <code class="computeroutput"><span class="identifier">optional</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
|
|
is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is initialized and its value is a <span class="emphasis"><em>copy</em></span> of the value
|
|
of <code class="computeroutput"><span class="identifier">rhs</span></code>; else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is
|
|
uninitialized.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="keyword">operator</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&)</span></code>
|
|
or <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span>
|
|
<span class="keyword">const</span><span class="special">&</span>
|
|
<span class="special">)</span></code> throws.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> If both <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="identifier">rhs</span></code>
|
|
are initially initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s
|
|
<span class="emphasis"><em>assignment operator</em></span> is used. If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initially initialized but <code class="computeroutput"><span class="identifier">rhs</span></code> is uninitialized, <code class="computeroutput"><span class="identifier">T</span></code>'s
|
|
[destructor] is called. If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initially uninitialized but <code class="computeroutput"><span class="identifier">rhs</span></code> is initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s
|
|
<span class="emphasis"><em>copy constructor</em></span> is called.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Exception Safety:</strong></span> In the event of an exception,
|
|
the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is unchanged and its value unspecified
|
|
as far as optional is concerned (it is up to <code class="computeroutput"><span class="identifier">T</span></code>'s
|
|
<code class="computeroutput"><span class="keyword">operator</span><span class="special">=()</span></code>).
|
|
If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is initially uninitialized and <code class="computeroutput"><span class="identifier">T</span></code>'s
|
|
<span class="emphasis"><em>copy constructor</em></span> fails, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is left properly uninitialized.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
|
|
|
|
<span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">def</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">def</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="comment">// previous value (copy of 'v') destroyed from within 'opt'.</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span>
|
|
<span class="keyword">const</span><span class="special">&</span>
|
|
<span class="identifier">rhs</span> <span class="special">)</span>
|
|
<span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Effect:</strong></span> (Re)binds thee wrapped reference.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized and it references the
|
|
same object referenced by <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>; otherwise, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is uninitialized (and references no
|
|
object).
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> was initialized and so is <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>,
|
|
<code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is <span class="emphasis"><em>rebound</em></span> to the new object. See <a class="link" href="tutorial/rebinding_semantics_for_assignment_of_optional_references.html" title="Rebinding semantics for assignment of optional references">here</a>
|
|
for details on this behavior.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span>
|
|
<span class="keyword">int</span> <span class="identifier">b</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span>
|
|
<span class="identifier">T</span><span class="special">&</span> <span class="identifier">ra</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span>
|
|
<span class="identifier">T</span><span class="special">&</span> <span class="identifier">rb</span> <span class="special">=</span> <span class="identifier">b</span> <span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">def</span> <span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">ora</span><span class="special">(</span><span class="identifier">ra</span><span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">orb</span><span class="special">(</span><span class="identifier">rb</span><span class="special">)</span> <span class="special">;</span>
|
|
|
|
<span class="identifier">def</span> <span class="special">=</span> <span class="identifier">orb</span> <span class="special">;</span> <span class="comment">// binds 'def' to 'b' through 'rb' wrapped within 'orb'</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">b</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="special">*</span><span class="identifier">def</span> <span class="special">=</span> <span class="identifier">ora</span> <span class="special">;</span> <span class="comment">// changes the value of 'b' to a copy of the value of 'a'</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">b</span> <span class="special">==</span> <span class="identifier">a</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="keyword">int</span> <span class="identifier">c</span> <span class="special">=</span> <span class="number">3</span><span class="special">;</span>
|
|
<span class="keyword">int</span><span class="special">&</span> <span class="identifier">rc</span> <span class="special">=</span> <span class="identifier">c</span> <span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">orc</span><span class="special">(</span><span class="identifier">rc</span><span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">ora</span> <span class="special">=</span> <span class="identifier">orc</span> <span class="special">;</span> <span class="comment">// REBINDS ora to 'c' through 'rc'</span>
|
|
<span class="identifier">c</span> <span class="special">=</span> <span class="number">4</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">ora</span> <span class="special">==</span> <span class="number">4</span> <span class="special">)</span> <span class="special">;</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_optional_operator_move_equal_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&&</span> <span class="identifier">rhs</span>
|
|
<span class="special">)</span> <span class="keyword">noexcept</span><span class="special">(</span></code><span class="emphasis"><em>see below</em></span><code class="computeroutput"><span class="special">);</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Effect:</strong></span> Move-assigns another <code class="computeroutput"><span class="identifier">optional</span></code> to an <code class="computeroutput"><span class="identifier">optional</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
|
|
is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is initialized and its value is moved from <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>, <code class="computeroutput"><span class="identifier">rhs</span></code>
|
|
remains initialized; else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is uninitialized.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="keyword">operator</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span>
|
|
<span class="special">)</span></code> or <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span>
|
|
<span class="identifier">T</span> <span class="special">&&</span>
|
|
<span class="special">)</span></code> throws.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> If both <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="identifier">rhs</span></code>
|
|
are initially initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s
|
|
<span class="emphasis"><em>move assignment operator</em></span> is used. If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is
|
|
initially initialized but <code class="computeroutput"><span class="identifier">rhs</span></code>
|
|
is uninitialized, <code class="computeroutput"><span class="identifier">T</span></code>'s [destructor]
|
|
is called. If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is initially uninitialized but <code class="computeroutput"><span class="identifier">rhs</span></code>
|
|
is initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s <span class="emphasis"><em>move
|
|
constructor</em></span> is called. The expression inside <code class="computeroutput"><span class="keyword">noexcept</span></code>
|
|
is equivalent to <code class="computeroutput"><span class="identifier">is_nothrow_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span>
|
|
<span class="special">&&</span> <span class="identifier">is_nothrow_move_assignable</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Exception Safety:</strong></span> In the event of an exception,
|
|
the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is unchanged and its value unspecified
|
|
as far as optional is concerned (it is up to <code class="computeroutput"><span class="identifier">T</span></code>'s
|
|
<code class="computeroutput"><span class="keyword">operator</span><span class="special">=()</span></code>).
|
|
If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is initially uninitialized and <code class="computeroutput"><span class="identifier">T</span></code>'s
|
|
<span class="emphasis"><em>move constructor</em></span> fails, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is left properly uninitialized.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">))</span> <span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
|
|
|
|
<span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">def</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">def</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>&&</span>
|
|
<span class="identifier">rhs</span> <span class="special">)</span>
|
|
<span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
|
|
<span class="bold"><strong>Effect:</strong></span> Same as <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">)</span></code>.
|
|
</li></ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_optional_operator_equal_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">optional</span><span class="special">&</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span>
|
|
<span class="keyword">const</span><span class="special">&</span>
|
|
<span class="identifier">rhs</span> <span class="special">)</span>
|
|
<span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Effect:</strong></span> Assigns another convertible optional
|
|
to an optional.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
|
|
is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is initialized and its value is a <span class="emphasis"><em>copy</em></span> of the value
|
|
of <code class="computeroutput"><span class="identifier">rhs</span></code> <span class="emphasis"><em>converted</em></span>
|
|
to type <code class="computeroutput"><span class="identifier">T</span></code>; else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is
|
|
uninitialized.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">U</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span></code> or <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span>
|
|
<span class="identifier">U</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span></code>
|
|
throws.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> If both <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and rhs are initially initialized,
|
|
<code class="computeroutput"><span class="identifier">T</span></code>'s <span class="emphasis"><em>assignment
|
|
operator</em></span> (from <code class="computeroutput"><span class="identifier">U</span></code>)
|
|
is used. If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is initially initialized but <code class="computeroutput"><span class="identifier">rhs</span></code>
|
|
is uninitialized, <code class="computeroutput"><span class="identifier">T</span></code>'s
|
|
<span class="emphasis"><em>destructor</em></span> is called. If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initially uninitialized but rhs
|
|
is initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s <span class="emphasis"><em>converting
|
|
constructor</em></span> (from <code class="computeroutput"><span class="identifier">U</span></code>)
|
|
is called.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Exception Safety:</strong></span> In the event of an exception,
|
|
the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is unchanged and its value unspecified
|
|
as far as optional is concerned (it is up to <code class="computeroutput"><span class="identifier">T</span></code>'s
|
|
<code class="computeroutput"><span class="keyword">operator</span><span class="special">=()</span></code>).
|
|
If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is initially uninitialized and <code class="computeroutput"><span class="identifier">T</span></code>'s
|
|
converting constructor fails, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is left properly uninitialized.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt0</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">opt1</span><span class="special">;</span>
|
|
|
|
<span class="identifier">opt1</span> <span class="special">=</span> <span class="identifier">opt0</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt1</span> <span class="special">==</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="identifier">U</span><span class="special">>(</span><span class="identifier">v</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_optional_operator_move_equal_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">optional</span><span class="special">&</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">>&&</span>
|
|
<span class="identifier">rhs</span> <span class="special">)</span>
|
|
<span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Effect:</strong></span> Move-assigns another convertible
|
|
optional to an optional.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
|
|
is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is initialized and its value is moved from the value of <code class="computeroutput"><span class="identifier">rhs</span></code>;
|
|
else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is uninitialized.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">U</span><span class="special">&&</span> <span class="special">)</span></code>
|
|
or <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span> <span class="special">)</span></code>
|
|
throws.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> If both <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="identifier">rhs</span></code>
|
|
are initially initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s
|
|
<span class="emphasis"><em>assignment operator</em></span> (from <code class="computeroutput"><span class="identifier">U</span><span class="special">&&</span></code>) is used. If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initially initialized but <code class="computeroutput"><span class="identifier">rhs</span></code> is uninitialized, <code class="computeroutput"><span class="identifier">T</span></code>'s
|
|
<span class="emphasis"><em>destructor</em></span> is called. If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initially uninitialized but <code class="computeroutput"><span class="identifier">rhs</span></code> is initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s
|
|
<span class="emphasis"><em>converting constructor</em></span> (from <code class="computeroutput"><span class="identifier">U</span><span class="special">&&</span></code>) is called.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Exception Safety:</strong></span> In the event of an exception,
|
|
the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is unchanged and its value unspecified
|
|
as far as optional is concerned (it is up to <code class="computeroutput"><span class="identifier">T</span></code>'s
|
|
<code class="computeroutput"><span class="keyword">operator</span><span class="special">=()</span></code>).
|
|
If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is initially uninitialized and <code class="computeroutput"><span class="identifier">T</span></code>'s
|
|
converting constructor fails, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is left properly uninitialized.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt0</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">opt1</span><span class="special">;</span>
|
|
|
|
<span class="identifier">opt1</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">opt0</span><span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt1</span> <span class="special">==</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="identifier">U</span><span class="special">>(</span><span class="identifier">v</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_optional_emplace"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">></span> <span class="keyword">void</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
|
|
<span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">emplace</span><span class="special">(</span> <span class="identifier">Args</span><span class="special">...&&</span>
|
|
<span class="identifier">args</span> <span class="special">);</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Requires:</strong></span> The compiler supports rvalue
|
|
references and variadic templates.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Effect:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized calls <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span> <span class="special">=</span>
|
|
<span class="identifier">none</span></code>. Then initializes in-place
|
|
the contained value as if direct-initializing an object of type <code class="computeroutput"><span class="identifier">T</span></code> with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special"><</span><span class="identifier">Args</span><span class="special">>(</span><span class="identifier">args</span><span class="special">)...</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Whatever the selected <code class="computeroutput"><span class="identifier">T</span></code>'s constructor throws.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
|
|
need not be <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>
|
|
or <code class="computeroutput"><span class="identifier">MoveAssignable</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Exception Safety:</strong></span> If an exception is thrown
|
|
during the initialization of <code class="computeroutput"><span class="identifier">T</span></code>,
|
|
<code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is <span class="emphasis"><em>uninitialized</em></span>.
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_optional_operator_equal_factory"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">InPlaceFactory</span><span class="special">></span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">InPlaceFactory</span>
|
|
<span class="keyword">const</span><span class="special">&</span>
|
|
<span class="identifier">f</span> <span class="special">);</span></code>
|
|
</p></blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">TypedInPlaceFactory</span><span class="special">></span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">TypedInPlaceFactory</span>
|
|
<span class="keyword">const</span><span class="special">&</span>
|
|
<span class="identifier">f</span> <span class="special">);</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Effect:</strong></span> Assigns an <code class="computeroutput"><span class="identifier">optional</span></code>
|
|
with a value of <code class="computeroutput"><span class="identifier">T</span></code> obtained
|
|
from the factory.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>
|
|
and its value is <span class="emphasis"><em>directly given</em></span> from the factory
|
|
<code class="computeroutput"><span class="identifier">f</span></code> (i.e., the value <span class="underline">is not copied</span>).
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Whatever the <code class="computeroutput"><span class="identifier">T</span></code>
|
|
constructor called by the factory throws.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> See <a class="link" href="tutorial/in_place_factories.html" title="In-Place Factories">In-Place
|
|
Factories</a>
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
|
|
be thrown during the call to the <code class="computeroutput"><span class="identifier">T</span></code>
|
|
constructor used by the factory; in that case, the <code class="computeroutput"><span class="identifier">optional</span></code>
|
|
object will be reset to be <span class="emphasis"><em>uninitialized</em></span>.
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_optional_reset_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">void</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
|
|
<span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">reset</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
|
|
<span class="bold"><strong>Deprecated:</strong></span> same as <code class="computeroutput"><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span>
|
|
<span class="keyword">const</span><span class="special">&</span>
|
|
<span class="identifier">v</span><span class="special">)</span>
|
|
<span class="special">;</span></code>
|
|
</li></ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_optional_reset"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">void</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">reset</span><span class="special">()</span> <span class="keyword">noexcept</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
|
|
<span class="bold"><strong>Deprecated:</strong></span> Same as <code class="computeroutput"><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">none_t</span> <span class="special">);</span></code>
|
|
</li></ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_optional_get"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
|
|
<span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">T</span><span class="special">&</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get</span><span class="special">()</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span>
|
|
<span class="keyword">const</span><span class="special">&</span>
|
|
<span class="identifier">get</span> <span class="special">(</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">get</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
|
|
<span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span>
|
|
<span class="special">&)</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Returns:</strong></span> A reference to the contained
|
|
value
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> The requirement is asserted via
|
|
<code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>.
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">get</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">T</span><span class="special">&</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">get</span><span class="special">()</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span>
|
|
<span class="keyword">const</span><span class="special">&</span>
|
|
<span class="identifier">get</span> <span class="special">(</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">get</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span>
|
|
<span class="special">&)</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Requires: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Returns:</strong></span> <span class="underline">The</span>
|
|
reference contained.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> The requirement is asserted via
|
|
<code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>.
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_optional_operator_asterisk"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
|
|
<span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">*()</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">T</span><span class="special">&</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">*()</span> <span class="special">&;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">T</span><span class="special">&&</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">*()</span> <span class="special">&&;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Returns:</strong></span> A reference to the contained
|
|
value
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> The requirement is asserted via
|
|
<code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>.
|
|
On compilers that do not support ref-qualifiers on member functions these
|
|
three overloads are replaced with the classical two: a <code class="computeroutput"><span class="keyword">const</span></code>
|
|
and non-<code class="computeroutput"><span class="keyword">const</span></code> member functions.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span> <span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">v</span> <span class="special">);</span>
|
|
<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">u</span> <span class="special">=</span> <span class="special">*</span><span class="identifier">opt</span><span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">u</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">T</span> <span class="identifier">w</span> <span class="special">;</span>
|
|
<span class="special">*</span><span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">w</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">w</span> <span class="special">)</span> <span class="special">;</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">*()</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">T</span> <span class="special">&</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">*()</span> <span class="special">&</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">T</span> <span class="special">&</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">*()</span> <span class="special">&&</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Requires: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Returns:</strong></span> <span class="underline">The</span>
|
|
reference contained.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> The requirement is asserted via
|
|
<code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>.
|
|
On compilers that do not support ref-qualifiers on member functions these
|
|
three overloads are replaced with the classical two: a <code class="computeroutput"><span class="keyword">const</span></code>
|
|
and non-<code class="computeroutput"><span class="keyword">const</span></code> member functions.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span> <span class="special">;</span>
|
|
<span class="identifier">T</span><span class="special">&</span> <span class="identifier">vref</span> <span class="special">=</span> <span class="identifier">v</span> <span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">vref</span> <span class="special">);</span>
|
|
<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">vref2</span> <span class="special">=</span> <span class="special">*</span><span class="identifier">opt</span><span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">vref2</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="special">++</span> <span class="identifier">v</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_optional_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span><span class="special">()</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">T</span><span class="special">&</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span><span class="special">()</span> <span class="special">&</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">T</span><span class="special">&&</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span><span class="special">()</span> <span class="special">&&</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Returns:</strong></span> A reference to the contained
|
|
value, if <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is initialized.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> An instance of <code class="computeroutput"><span class="identifier">bad_optional_access</span></code>,
|
|
if <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
|
is not initialized.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> On compilers that do not support
|
|
ref-qualifiers on member functions these three overloads are replaced with
|
|
the classical two: a <code class="computeroutput"><span class="keyword">const</span></code>
|
|
and non-<code class="computeroutput"><span class="keyword">const</span></code> member functions.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span> <span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o0</span><span class="special">,</span> <span class="identifier">o1</span> <span class="special">(</span> <span class="identifier">v</span> <span class="special">);</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span><span class="special">.</span><span class="identifier">value</span><span class="special">()</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">);</span>
|
|
|
|
<span class="keyword">try</span> <span class="special">{</span>
|
|
<span class="identifier">o0</span><span class="special">.</span><span class="identifier">value</span><span class="special">();</span> <span class="comment">// throws</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="keyword">false</span> <span class="special">);</span>
|
|
<span class="special">}</span>
|
|
<span class="keyword">catch</span><span class="special">(</span><span class="identifier">bad_optional_access</span><span class="special">&)</span> <span class="special">{</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="keyword">true</span> <span class="special">);</span>
|
|
<span class="special">}</span>
|
|
</pre>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</li>
|
|
</ul></div>
|
|
<a name="reference_optional_value_or"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value_or</span><span class="special">(</span><span class="identifier">U</span> <span class="special">&&</span>
|
|
<span class="identifier">v</span><span class="special">)</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value_or</span><span class="special">(</span><span class="identifier">U</span> <span class="special">&&</span>
|
|
<span class="identifier">v</span><span class="special">)</span> <span class="special">&&</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
|
|
is CopyConstructible.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Returns:</strong></span> First overload: <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">?</span> <span class="special">**</span><span class="keyword">this</span> <span class="special">:</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="identifier">forward</span><span class="special"><</span><span class="identifier">U</span><span class="special">>(</span><span class="identifier">v</span><span class="special">))</span></code>.
|
|
second overload: <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">?</span>
|
|
<span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(**</span><span class="keyword">this</span><span class="special">)</span> <span class="special">:</span>
|
|
<span class="keyword">static_cast</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="identifier">forward</span><span class="special"><</span><span class="identifier">U</span><span class="special">>(</span><span class="identifier">v</span><span class="special">))</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Any exception thrown by the selected
|
|
constructor of <code class="computeroutput"><span class="identifier">T</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> On compilers that do not support
|
|
ref-qualifiers on member functions these three overloads are replaced with
|
|
the classical two: a <code class="computeroutput"><span class="keyword">const</span></code>
|
|
and non-<code class="computeroutput"><span class="keyword">const</span></code> member functions.
|
|
On compilers without rvalue reference support the type of <code class="computeroutput"><span class="identifier">v</span></code> becomes <code class="computeroutput"><span class="identifier">U</span>
|
|
<span class="keyword">const</span><span class="special">&</span></code>.
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_optional_get_value_or_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
|
|
<span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get_value_or</span><span class="special">(</span>
|
|
<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="keyword">default</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">T</span><span class="special">&</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get_value_or</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&</span>
|
|
<span class="keyword">default</span> <span class="special">)</span>
|
|
<span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span>
|
|
<span class="keyword">const</span><span class="special">&</span>
|
|
<span class="identifier">get_optional_value_or</span> <span class="special">(</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">o</span><span class="special">,</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="keyword">default</span> <span class="special">)</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">get_optional_value_or</span>
|
|
<span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
|
|
<span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>&</span>
|
|
<span class="identifier">o</span><span class="special">,</span> <span class="identifier">T</span><span class="special">&</span> <span class="keyword">default</span> <span class="special">)</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Deprecated:</strong></span> Use <code class="computeroutput"><span class="identifier">value_or</span><span class="special">()</span></code> instead.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Returns:</strong></span> A reference to the contained
|
|
value, if any, or <code class="computeroutput"><span class="keyword">default</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">,</span> <span class="identifier">z</span> <span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span><span class="special">;</span>
|
|
<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">=</span> <span class="identifier">def</span><span class="special">.</span><span class="identifier">get_value_or</span><span class="special">(</span><span class="identifier">z</span><span class="special">);</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">y</span> <span class="special">==</span> <span class="identifier">z</span> <span class="special">)</span> <span class="special">;</span>
|
|
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">v</span> <span class="special">);</span>
|
|
<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">u</span> <span class="special">=</span> <span class="identifier">get_optional_value_or</span><span class="special">(</span><span class="identifier">opt</span><span class="special">,</span><span class="identifier">z</span><span class="special">);</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">u</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">u</span> <span class="special">!=</span> <span class="identifier">z</span> <span class="special">)</span> <span class="special">;</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_optional_get_ptr"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
|
|
<span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get_ptr</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">T</span><span class="special">*</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span>
|
|
<span class="keyword">const</span><span class="special">*</span> <span class="identifier">get_pointer</span> <span class="special">(</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span><span class="special">*</span> <span class="identifier">get_pointer</span>
|
|
<span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
|
|
<span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span>
|
|
<span class="special">&)</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Returns:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized, a pointer to the contained
|
|
value; else <code class="computeroutput"><span class="number">0</span></code> (<span class="emphasis"><em>null</em></span>).
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> The contained value is permanently
|
|
stored within <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>,
|
|
so you should not hold nor delete this pointer
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span> <span class="identifier">copt</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
|
|
<span class="identifier">T</span><span class="special">*</span> <span class="identifier">p</span> <span class="special">=</span> <span class="identifier">opt</span><span class="special">.</span><span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">;</span>
|
|
<span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">cp</span> <span class="special">=</span> <span class="identifier">copt</span><span class="special">.</span><span class="identifier">get_ptr</span><span class="special">();</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">p</span> <span class="special">==</span> <span class="identifier">get_pointer</span><span class="special">(</span><span class="identifier">opt</span><span class="special">)</span> <span class="special">);</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">cp</span> <span class="special">==</span> <span class="identifier">get_pointer</span><span class="special">(</span><span class="identifier">copt</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_optional_operator_arrow"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
|
|
<span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span> <span class="special">->()</span>
|
|
<span class="keyword">const</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">T</span><span class="special">*</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span> <span class="special">->()</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Requires: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Returns:</strong></span> A pointer to the contained value.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> The requirement is asserted via
|
|
<code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">X</span> <span class="special">{</span> <span class="keyword">int</span> <span class="identifier">mdata</span> <span class="special">;</span> <span class="special">}</span> <span class="special">;</span>
|
|
<span class="identifier">X</span> <span class="identifier">x</span> <span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">X</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">(</span><span class="identifier">x</span><span class="special">);</span>
|
|
<span class="identifier">opt</span><span class="special">-></span><span class="identifier">mdata</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_optional_operator_bool"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span> <span class="keyword">bool</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">!=</span> <span class="number">0</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> On compilers that do not support
|
|
explicit conversion operators this falls back to safe-bool idiom.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">def</span> <span class="special">==</span> <span class="number">0</span> <span class="special">);</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt</span> <span class="special">);</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt</span> <span class="special">!=</span> <span class="number">0</span> <span class="special">);</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_optional_operator_not"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">bool</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">!()</span> <span class="keyword">noexcept</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Returns:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is uninitialized, <code class="computeroutput"><span class="keyword">true</span></code>;
|
|
else <code class="computeroutput"><span class="keyword">false</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> This operator is provided for those
|
|
compilers which can't use the <span class="emphasis"><em>unspecified-bool-type operator</em></span>
|
|
in certain boolean contexts.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">opt</span> <span class="special">);</span>
|
|
<span class="special">*</span><span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">some_T</span> <span class="special">;</span>
|
|
|
|
<span class="comment">// Notice the "double-bang" idiom here.</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!!</span><span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_optional_is_initialized"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">bool</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">is_initialized</span><span class="special">()</span>
|
|
<span class="keyword">const</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
|
|
<span class="bold"><strong>Deprecated:</strong></span> Same as <code class="computeroutput"><span class="keyword">explicit</span>
|
|
<span class="keyword">operator</span> <span class="keyword">bool</span>
|
|
<span class="special">()</span> <span class="special">;</span></code>
|
|
</li></ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<h4>
|
|
<a name="boost_optional.detailed_semantics.h1"></a>
|
|
<span class="phrase"><a name="boost_optional.detailed_semantics.free_functions"></a></span><a class="link" href="detailed_semantics.html#boost_optional.detailed_semantics.free_functions">Free
|
|
functions</a>
|
|
</h4>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_make_optional_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> <span class="identifier">make_optional</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="identifier">v</span><span class="special">)</span></code> for the <span class="emphasis"><em>deduced</em></span> type
|
|
<code class="computeroutput"><span class="identifier">T</span></code> of <code class="computeroutput"><span class="identifier">v</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> <span class="keyword">void</span> <span class="identifier">foo</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span>
|
|
|
|
<span class="identifier">foo</span> <span class="special">(</span> <span class="identifier">make_optional</span><span class="special">(</span><span class="number">1</span><span class="special">+</span><span class="number">1</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> <span class="comment">// Creates an optional<int></span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_make_optional_bool_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> <span class="identifier">make_optional</span><span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="identifier">condition</span><span class="special">,</span><span class="identifier">v</span><span class="special">)</span></code>
|
|
for the <span class="emphasis"><em>deduced</em></span> type <code class="computeroutput"><span class="identifier">T</span></code>
|
|
of <code class="computeroutput"><span class="identifier">v</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">calculate_foo</span><span class="special">()</span>
|
|
<span class="special">{</span>
|
|
<span class="keyword">double</span> <span class="identifier">val</span> <span class="special">=</span> <span class="identifier">compute_foo</span><span class="special">();</span>
|
|
<span class="keyword">return</span> <span class="identifier">make_optional</span><span class="special">(</span><span class="identifier">is_not_nan_and_finite</span><span class="special">(</span><span class="identifier">val</span><span class="special">),</span><span class="identifier">val</span><span class="special">);</span>
|
|
<span class="special">}</span>
|
|
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">v</span> <span class="special">=</span> <span class="identifier">calculate_foo</span><span class="special">();</span>
|
|
<span class="keyword">if</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">v</span> <span class="special">)</span>
|
|
<span class="identifier">error</span><span class="special">(</span><span class="string">"foo wasn't computed"</span><span class="special">);</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_operator_compare_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
|
|
<span class="special">==</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span>
|
|
<span class="keyword">const</span><span class="special">&</span>
|
|
<span class="identifier">y</span> <span class="special">);</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
|
|
shall meet requirements of <code class="computeroutput"><span class="identifier">EqualityComparable</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Returns:</strong></span> If both <code class="computeroutput"><span class="identifier">x</span></code>
|
|
and <code class="computeroutput"><span class="identifier">y</span></code> are initialized,
|
|
<code class="computeroutput"><span class="special">(*</span><span class="identifier">x</span>
|
|
<span class="special">==</span> <span class="special">*</span><span class="identifier">y</span><span class="special">)</span></code>. If
|
|
only <code class="computeroutput"><span class="identifier">x</span></code> or <code class="computeroutput"><span class="identifier">y</span></code> is initialized, <code class="computeroutput"><span class="keyword">false</span></code>.
|
|
If both are uninitialized, <code class="computeroutput"><span class="keyword">true</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> Pointers have shallow relational
|
|
operators while <code class="computeroutput"><span class="identifier">optional</span></code>
|
|
has deep relational operators. Do not use <code class="computeroutput"><span class="keyword">operator</span>
|
|
<span class="special">==</span></code> directly in generic code which
|
|
expect to be given either an <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> or a pointer; use <a href="../../../../utility/OptionalPointee.html#equal" target="_top"><code class="computeroutput"><span class="identifier">equal_pointees</span><span class="special">()</span></code></a>
|
|
instead
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">(</span><span class="number">12</span><span class="special">);</span>
|
|
<span class="identifier">T</span> <span class="identifier">y</span><span class="special">(</span><span class="number">12</span><span class="special">);</span>
|
|
<span class="identifier">T</span> <span class="identifier">z</span><span class="special">(</span><span class="number">21</span><span class="special">);</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def0</span> <span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def1</span> <span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">optX</span><span class="special">(</span><span class="identifier">x</span><span class="special">);</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">optY</span><span class="special">(</span><span class="identifier">y</span><span class="special">);</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">optZ</span><span class="special">(</span><span class="identifier">z</span><span class="special">);</span>
|
|
|
|
<span class="comment">// Identity always hold</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">def0</span> <span class="special">==</span> <span class="identifier">def0</span> <span class="special">);</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">optX</span> <span class="special">==</span> <span class="identifier">optX</span> <span class="special">);</span>
|
|
|
|
<span class="comment">// Both uninitialized compare equal</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">def0</span> <span class="special">==</span> <span class="identifier">def1</span> <span class="special">);</span>
|
|
|
|
<span class="comment">// Only one initialized compare unequal.</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">def0</span> <span class="special">!=</span> <span class="identifier">optX</span> <span class="special">);</span>
|
|
|
|
<span class="comment">// Both initialized compare as (*lhs == *rhs)</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">optX</span> <span class="special">==</span> <span class="identifier">optY</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">optX</span> <span class="special">!=</span> <span class="identifier">optZ</span> <span class="special">)</span> <span class="special">;</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_operator_compare_less_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
|
|
<span class="special"><</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span>
|
|
<span class="keyword">const</span><span class="special">&</span>
|
|
<span class="identifier">y</span> <span class="special">);</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
|
|
shall meet requirements of <code class="computeroutput"><span class="identifier">LessThanComparable</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Returns:</strong></span> If <code class="computeroutput"><span class="identifier">y</span></code>
|
|
is not initialized, <code class="computeroutput"><span class="keyword">false</span></code>.
|
|
If <code class="computeroutput"><span class="identifier">y</span></code> is initialized and
|
|
<code class="computeroutput"><span class="identifier">x</span></code> is not initialized,
|
|
<code class="computeroutput"><span class="keyword">true</span></code>. If both <code class="computeroutput"><span class="identifier">x</span></code> and <code class="computeroutput"><span class="identifier">y</span></code>
|
|
are initialized, <code class="computeroutput"><span class="special">(*</span><span class="identifier">x</span>
|
|
<span class="special"><</span> <span class="special">*</span><span class="identifier">y</span><span class="special">)</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> Pointers have shallow relational
|
|
operators while <code class="computeroutput"><span class="identifier">optional</span></code>
|
|
has deep relational operators. Do not use <code class="computeroutput"><span class="keyword">operator</span>
|
|
<span class="special"><</span></code> directly in generic code which
|
|
expect to be given either an <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> or a pointer; use <a href="../../../../utility/OptionalPointee.html#less" target="_top"><code class="computeroutput"><span class="identifier">less_pointees</span><span class="special">()</span></code></a>
|
|
instead.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">(</span><span class="number">12</span><span class="special">);</span>
|
|
<span class="identifier">T</span> <span class="identifier">y</span><span class="special">(</span><span class="number">34</span><span class="special">);</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">optX</span><span class="special">(</span><span class="identifier">x</span><span class="special">);</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">optY</span><span class="special">(</span><span class="identifier">y</span><span class="special">);</span>
|
|
|
|
<span class="comment">// Identity always hold</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">def</span> <span class="special"><</span> <span class="identifier">def</span><span class="special">)</span> <span class="special">);</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">optX</span> <span class="special">==</span> <span class="identifier">optX</span> <span class="special">);</span>
|
|
|
|
<span class="comment">// Both uninitialized compare equal</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">def0</span> <span class="special">==</span> <span class="identifier">def1</span> <span class="special">);</span>
|
|
|
|
<span class="comment">// Only one initialized compare unequal.</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">def0</span> <span class="special">!=</span> <span class="identifier">optX</span> <span class="special">);</span>
|
|
|
|
<span class="comment">// Both initialized compare as (*lhs == *rhs)</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">optX</span> <span class="special">==</span> <span class="identifier">optY</span> <span class="special">)</span> <span class="special">;</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">optX</span> <span class="special">!=</span> <span class="identifier">optZ</span> <span class="special">)</span> <span class="special">;</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
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</p>
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<a name="reference_operator_compare_not_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
|
|
<span class="special">!=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span>
|
|
<span class="keyword">const</span><span class="special">&</span>
|
|
<span class="identifier">y</span> <span class="special">);</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span>
|
|
<span class="identifier">x</span> <span class="special">==</span>
|
|
<span class="identifier">y</span> <span class="special">);</span></code>
|
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</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
|
</li>
|
|
</ul></div>
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|
<p>
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|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
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</p>
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<a name="reference_operator_compare_greater_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
|
|
<span class="special">></span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span>
|
|
<span class="keyword">const</span><span class="special">&</span>
|
|
<span class="identifier">y</span> <span class="special">);</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">(</span>
|
|
<span class="identifier">y</span> <span class="special"><</span>
|
|
<span class="identifier">x</span> <span class="special">);</span></code>
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|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
|
</li>
|
|
</ul></div>
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|
<p>
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|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
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|
</p>
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<a name="reference_operator_compare_less_or_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
|
|
<span class="special"><=</span> <span class="special">(</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span>
|
|
<span class="keyword">const</span><span class="special">&</span>
|
|
<span class="identifier">y</span> <span class="special">);</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span>
|
|
<span class="identifier">y</span> <span class="special"><</span>
|
|
<span class="identifier">x</span> <span class="special">);</span></code>
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_operator_compare_greater_or_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
|
|
<span class="special">>=</span> <span class="special">(</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span>
|
|
<span class="keyword">const</span><span class="special">&</span>
|
|
<span class="identifier">y</span> <span class="special">);</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span>
|
|
<span class="identifier">x</span><span class="special"><</span><span class="identifier">y</span> <span class="special">);</span></code>
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
|
</li>
|
|
</ul></div>
|
|
<a name="reference_operator_compare_equal_optional_none"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
|
|
<span class="special">==</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">none_t</span>
|
|
<span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">!</span><span class="identifier">x</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
|
|
need not meet requirements of <code class="computeroutput"><span class="identifier">EqualityComparable</span></code>.
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_operator_compare_not_equal_optional_none"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
|
|
<span class="special">!=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">none_t</span>
|
|
<span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
|
|
<span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span>
|
|
<span class="identifier">x</span> <span class="special">==</span>
|
|
<span class="identifier">y</span> <span class="special">);</span></code>
|
|
</li></ul></div>
|
|
<p>
|
|
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
|
</p>
|
|
<a name="reference_swap_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
|
<code class="computeroutput"><span class="keyword">void</span> <span class="identifier">swap</span>
|
|
<span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span>
|
|
<span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span></code>
|
|
</p></blockquote></div>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Effect:</strong></span> If both <code class="computeroutput"><span class="identifier">x</span></code>
|
|
and <code class="computeroutput"><span class="identifier">y</span></code> are initialized,
|
|
calls <code class="computeroutput"><span class="identifier">swap</span><span class="special">(*</span><span class="identifier">x</span><span class="special">,*</span><span class="identifier">y</span><span class="special">)</span></code> using <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">swap</span></code>.
|
|
If only one is initialized, say <code class="computeroutput"><span class="identifier">x</span></code>,
|
|
calls: <code class="computeroutput"><span class="identifier">y</span><span class="special">.</span><span class="identifier">reset</span><span class="special">(*</span><span class="identifier">x</span><span class="special">);</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">reset</span><span class="special">();</span></code> If none is initialized, does nothing.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Postconditions:</strong></span> The states of <code class="computeroutput"><span class="identifier">x</span></code> and <code class="computeroutput"><span class="identifier">y</span></code>
|
|
interchanged.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Throws:</strong></span> If both are initialized, whatever
|
|
<code class="computeroutput"><span class="identifier">swap</span><span class="special">(</span><span class="identifier">T</span><span class="special">&,</span><span class="identifier">T</span><span class="special">&)</span></code>
|
|
throws. If only one is initialized, whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span>
|
|
<span class="special">)</span></code> throws.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Notes:</strong></span> If both are initialized, <code class="computeroutput"><span class="identifier">swap</span><span class="special">(</span><span class="identifier">T</span><span class="special">&,</span><span class="identifier">T</span><span class="special">&)</span></code>
|
|
is used unqualified but with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">swap</span></code>
|
|
introduced in scope. If only one is initialized, <code class="computeroutput"><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code> and <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span>
|
|
<span class="identifier">T</span><span class="special">&&</span>
|
|
<span class="special">)</span></code> is called.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Exception Safety:</strong></span> If both are initialized,
|
|
this operation has the exception safety guarantees of <code class="computeroutput"><span class="identifier">swap</span><span class="special">(</span><span class="identifier">T</span><span class="special">&,</span><span class="identifier">T</span><span class="special">&)</span></code>.
|
|
If only one is initialized, it has the same basic guarantee as <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span>
|
|
<span class="special">)</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
<span class="bold"><strong>Example:</strong></span>
|
|
<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">(</span><span class="number">12</span><span class="special">);</span>
|
|
<span class="identifier">T</span> <span class="identifier">y</span><span class="special">(</span><span class="number">21</span><span class="special">);</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def0</span> <span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def1</span> <span class="special">;</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">optX</span><span class="special">(</span><span class="identifier">x</span><span class="special">);</span>
|
|
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">optY</span><span class="special">(</span><span class="identifier">y</span><span class="special">);</span>
|
|
|
|
<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">def0</span><span class="special">,</span><span class="identifier">def1</span><span class="special">);</span> <span class="comment">// no-op</span>
|
|
|
|
<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">def0</span><span class="special">,</span><span class="identifier">optX</span><span class="special">);</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def0</span> <span class="special">==</span> <span class="identifier">x</span> <span class="special">);</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">optX</span> <span class="special">);</span>
|
|
|
|
<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">def0</span><span class="special">,</span><span class="identifier">optX</span><span class="special">);</span> <span class="comment">// Get back to original values</span>
|
|
|
|
<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">optX</span><span class="special">,</span><span class="identifier">optY</span><span class="special">);</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">optX</span> <span class="special">==</span> <span class="identifier">y</span> <span class="special">);</span>
|
|
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">optY</span> <span class="special">==</span> <span class="identifier">x</span> <span class="special">);</span>
|
|
</pre>
|
|
</li>
|
|
</ul></div>
|
|
</div>
|
|
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
|
<td align="left"></td>
|
|
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014 Andrzej Krzemieński<p>
|
|
Distributed under the Boost Software License, Version 1.0. (See accompanying
|
|
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
|
|
</p>
|
|
</div></td>
|
|
</tr></table>
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<hr>
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