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<div class="section">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="boost_localfunction.alternatives"></a><a class="link" href="alternatives.html" title="Annex: Alternatives">Annex: Alternatives</a>
</h2></div></div></div>
<p>
This section compares the features offered by this library with similar features
offered by C++ and by other libraries.
</p>
<h4>
<a name="boost_localfunction.alternatives.h0"></a>
<span class="phrase"><a name="boost_localfunction.alternatives.features"></a></span><a class="link" href="alternatives.html#boost_localfunction.alternatives.features">Features</a>
</h4>
<p>
The following table compares local function features.
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Local Function Feature
</p>
</th>
<th>
<p>
Boost.LocalFunction
</p>
</th>
<th>
<p>
C++11 Lambda Function (Not C++03)
</p>
</th>
<th>
<p>
Local Functor
</p>
</th>
<th>
<p>
Global Functor (Not Local)
</p>
</th>
<th>
<p>
Boost.Phoenix
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<span class="emphasis"><em>Can be defined locally</em></span>
</p>
</td>
<td>
<p>
Yes.
</p>
</td>
<td>
<p>
Yes.
</p>
</td>
<td>
<p>
Yes.
</p>
</td>
<td>
<p>
No. Therefore this not really an alternative implementation of local
functions but it is listed here just for comparison.
</p>
</td>
<td>
<p>
Yes.
</p>
</td>
</tr>
<tr>
<td>
<p>
<span class="emphasis"><em>Can be defined using C++ statement syntax</em></span>
</p>
</td>
<td>
<p>
Yes. Plus eventual compiler errors and debugging retain their usual
meaning and format.
</p>
</td>
<td>
<p>
Yes. Plus eventual compiler errors and debugging retain their usual
meaning and format.
</p>
</td>
<td>
<p>
Yes. Plus eventual compiler errors and debugging retain their usual
meaning and format.
</p>
</td>
<td>
<p>
Yes. Plus eventual compiler errors and debugging retain their usual
meaning and format.
</p>
</td>
<td>
<p>
No (it uses C++ <a href="http://en.wikibooks.org/wiki/More_C%2B%2B_Idioms/Expression-template" target="_top">expression
template</a> syntax).
</p>
</td>
</tr>
<tr>
<td>
<p>
<span class="emphasis"><em>Can be defined within expressions</em></span>
</p>
</td>
<td>
<p>
No. It can be defined only within declarations.
</p>
</td>
<td>
<p>
Yes (plus the local function can be unnamed).
</p>
</td>
<td>
<p>
No. It can be defined only within declarations.
</p>
</td>
<td>
<p>
No. It can be defined only within declarations.
</p>
</td>
<td>
<p>
Yes (plus the local function can be unnamed).
</p>
</td>
</tr>
<tr>
<td>
<p>
<span class="emphasis"><em>Can be passed as template parameter (e.g., to STL algorithms)</em></span>
</p>
</td>
<td>
<p>
Yes. The <a href="http://www.open-std.org/JTC1/SC22/WG21/docs/standards" target="_top">C++03</a>
standard does not allow to pass local types as template parameters
(see <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2657.htm" target="_top">[N2657]</a>)
but this library implements a "trick" to get around this
limitation (see the <a class="link" href="implementation.html" title="Annex: Implementation">Implementation</a>
section).
</p>
</td>
<td>
<p>
Yes.
</p>
</td>
<td>
<p>
No on <a href="http://www.open-std.org/JTC1/SC22/WG21/docs/standards" target="_top">C++03</a>
compilers (but yes on <a href="http://www.open-std.org/JTC1/SC22/WG21/" target="_top">C++11</a>
compilers and some compilers like MSVC 8.0, see <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2657.htm" target="_top">[N2657]</a>).
</p>
</td>
<td>
<p>
Yes.
</p>
</td>
<td>
<p>
Yes.
</p>
</td>
</tr>
<tr>
<td>
<p>
<span class="emphasis"><em>Access variables in scope</em></span>
</p>
</td>
<td>
<p>
Yes. The variable names are repeated in the function declaration
so they can be bound by value, by constant value, by reference, and
by constant reference (the object <code class="computeroutput"><span class="keyword">this</span></code>
can also be bound using <code class="computeroutput"><span class="identifier">this_</span></code>).
</p>
</td>
<td>
<p>
Yes. The variable names are repeated in the function declaration
(plus there is a short-hand syntax to bind all variables in scope
at once) so they can be bound by constant value and by reference
(the object <code class="computeroutput"><span class="keyword">this</span></code> can
also be bound). However, variables cannot be bound by constant references
(see below).
</p>
</td>
<td>
<p>
No. Programmers must manually program functor data members and explicitly
specify their types to access variables in scope.
</p>
</td>
<td>
<p>
No. Programmers must manually program functor data members and explicitly
specify their types to access variables in scope.
</p>
</td>
<td>
<p>
Yes. Variables in scope are accessible as usual within expressions
(plus <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">phoenix</span><span class="special">::</span><span class="identifier">let</span></code> can be used to bind variables
by constant reference).
</p>
</td>
</tr>
<tr>
<td>
<p>
<span class="emphasis"><em><a href="http://en.wikipedia.org/wiki/Type_polymorphism#Parametric_polymorphism" target="_top">Polymorphic</a>
in the function parameter type</em></span>
</p>
</td>
<td>
<p>
No (local functions cannot be function templates).
</p>
</td>
<td>
<p>
No (<a href="http://www.open-std.org/JTC1/SC22/WG21/" target="_top">C++11</a>
lambdas cannot be function templates).
</p>
</td>
<td>
<p>
No (local classes cannot have member function templates).
</p>
</td>
<td>
<p>
Yes.
</p>
</td>
<td>
<p>
Yes.
</p>
</td>
</tr>
</tbody>
</table></div>
<p>
<span class="bold"><strong>C++11 Lambda Function</strong></span>
</p>
<p>
<a href="http://en.wikipedia.org/wiki/C%2B%2B0x#Lambda_functions_and_expressions" target="_top">C++11
lambda functions</a> have most of the features of this library plus some
additional feature (see also the example in the <a class="link" href="../index.html#boost_localfunction.introduction" title="Introduction">Introduction</a>
section):
</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<a href="http://en.wikipedia.org/wiki/C%2B%2B0x#Lambda_functions_and_expressions" target="_top">C++11
lambda functions</a> can be defined within expressions while this library
local functions can only be defined at declaration scope.
</li>
<li class="listitem">
<a href="http://en.wikipedia.org/wiki/C%2B%2B0x#Lambda_functions_and_expressions" target="_top">C++11
lambda functions</a> are only supported by the <a href="http://www.open-std.org/JTC1/SC22/WG21/" target="_top">C++11</a>
standard so they are not supported by all C++ compilers. This library local
functions can be programmed also on <a href="http://www.open-std.org/JTC1/SC22/WG21/docs/standards" target="_top">C++03</a>
compilers (and they have performances comparable to <a href="http://en.wikipedia.org/wiki/C%2B%2B0x#Lambda_functions_and_expressions" target="_top">C++11
lambda functions</a> on <a href="http://www.open-std.org/JTC1/SC22/WG21/" target="_top">C++11</a>
compilers).
</li>
<li class="listitem">
<a href="http://en.wikipedia.org/wiki/C%2B%2B0x#Lambda_functions_and_expressions" target="_top">C++11
lambda functions</a> do not allow to bind variables in scope by constant
reference. Because a variable cannot be bound by constant reference, <a href="http://en.wikipedia.org/wiki/C%2B%2B0x#Lambda_functions_and_expressions" target="_top">C++11
lambda functions</a> can bind a variable by constant only if the variable
is <code class="computeroutput"><span class="identifier">CopyConstructible</span></code> and
the binding requires a (potentially expensive) extra copy operation. Constant
reference binding is instead supported by this library.
</li>
<li class="listitem">
<a href="http://en.wikipedia.org/wiki/C%2B%2B0x#Lambda_functions_and_expressions" target="_top">C++11
lambda functions</a> do not allow to bind data members selectively
without binding also the object <code class="computeroutput"><span class="keyword">this</span></code>
while this library local functions can bind either selected data members
or the entire object <code class="computeroutput"><span class="keyword">this</span></code>
(using <code class="computeroutput"><span class="identifier">this_</span></code>).
</li>
<li class="listitem">
<a href="http://en.wikipedia.org/wiki/C%2B%2B0x#Lambda_functions_and_expressions" target="_top">C++11
lambda functions</a> provide a short-hand syntax to bind all variables
in scope at once (<code class="computeroutput"><span class="special">&amp;</span></code> or
<code class="computeroutput"><span class="special">=</span></code>) while this library local
function always require to bind variables naming them one-by-one.
</li>
</ul></div>
<p>
For example, for non-copyable objects (see also <a href="../../../example/noncopyable_cxx11_lambda_error.cpp" target="_top"><code class="literal">noncopyable_cxx11_lambda_error.cpp</code></a>
and <a href="../../../example/noncopyable_local_function.cpp" target="_top"><code class="literal">noncopyable_local_function.cpp</code></a>):
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
C++11 Lambda Function
</p>
</th>
<th>
<p>
Boost.LocalFunction
</p>
</th>
</tr></thead>
<tbody><tr>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">struct</span> <span class="identifier">n</span><span class="special">:</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">noncopyable</span> <span class="special">{</span>
<span class="keyword">int</span> <span class="identifier">i</span><span class="special">;</span>
<span class="identifier">n</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">_i</span><span class="special">):</span> <span class="identifier">i</span><span class="special">(</span><span class="identifier">_i</span><span class="special">)</span> <span class="special">{}</span>
<span class="special">};</span>
<span class="keyword">int</span> <span class="identifier">main</span><span class="special">(</span><span class="keyword">void</span><span class="special">)</span> <span class="special">{</span>
<span class="identifier">n</span> <span class="identifier">x</span><span class="special">(-</span><span class="number">1</span><span class="special">);</span>
<span class="keyword">auto</span> <span class="identifier">f</span> <span class="special">=</span> <span class="special">[</span><span class="identifier">x</span><span class="special">](</span><span class="keyword">void</span><span class="special">)</span> <span class="special">{</span> <span class="comment">// Error: x is non-copyable, but if</span>
<span class="identifier">assert</span><span class="special">(</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">i</span> <span class="special">==</span> <span class="special">-</span><span class="number">1</span><span class="special">);</span> <span class="comment">// bind `&amp;x` then `x` is not constant.</span>
<span class="special">};</span>
<span class="identifier">f</span><span class="special">();</span>
<span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
<span class="special">}</span>
</pre>
<p>
</p>
</td>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">struct</span> <span class="identifier">n</span><span class="special">:</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">noncopyable</span> <span class="special">{</span>
<span class="keyword">int</span> <span class="identifier">i</span><span class="special">;</span>
<span class="identifier">n</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">_i</span><span class="special">):</span> <span class="identifier">i</span><span class="special">(</span><span class="identifier">_i</span><span class="special">)</span> <span class="special">{}</span>
<span class="special">};</span>
<span class="identifier">BOOST_TYPEOF_REGISTER_TYPE</span><span class="special">(</span><span class="identifier">n</span><span class="special">)</span> <span class="comment">// Register for `bind&amp; x` below.</span>
<span class="keyword">int</span> <span class="identifier">main</span><span class="special">(</span><span class="keyword">void</span><span class="special">)</span> <span class="special">{</span>
<span class="identifier">n</span> <span class="identifier">x</span><span class="special">(-</span><span class="number">1</span><span class="special">);</span>
<span class="keyword">void</span> <span class="identifier">BOOST_LOCAL_FUNCTION</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">bind</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">)</span> <span class="special">{</span> <span class="comment">// OK: No copy</span>
<span class="identifier">assert</span><span class="special">(</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">i</span> <span class="special">==</span> <span class="special">-</span><span class="number">1</span><span class="special">);</span> <span class="comment">// and constant.</span>
<span class="special">}</span> <span class="identifier">BOOST_LOCAL_FUNCTION_NAME</span><span class="special">(</span><span class="identifier">f</span><span class="special">)</span>
<span class="identifier">f</span><span class="special">();</span>
<span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
<span class="special">}</span>
</pre>
<p>
</p>
</td>
</tr></tbody>
</table></div>
<p>
Or, for objects with expensive copy operations (see also <a href="../../../example/expensive_copy_cxx11_lambda.cpp" target="_top"><code class="literal">expensive_copy_cxx11_lambda.cpp</code></a>
and <a href="../../../example/expensive_copy_local_function.cpp" target="_top"><code class="literal">expensive_copy_local_function.cpp</code></a>):
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
C++11 Lambda Function
</p>
</th>
<th>
<p>
Boost.LocalFunction
</p>
</th>
</tr></thead>
<tbody><tr>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">struct</span> <span class="identifier">n</span> <span class="special">{</span>
<span class="keyword">int</span> <span class="identifier">i</span><span class="special">;</span>
<span class="identifier">n</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">_i</span><span class="special">):</span> <span class="identifier">i</span><span class="special">(</span><span class="identifier">_i</span><span class="special">)</span> <span class="special">{}</span>
<span class="identifier">n</span><span class="special">(</span><span class="identifier">n</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">):</span> <span class="identifier">i</span><span class="special">(</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">i</span><span class="special">)</span> <span class="special">{</span> <span class="comment">// Some time consuming copy operation.</span>
<span class="keyword">for</span> <span class="special">(</span><span class="keyword">unsigned</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> <span class="identifier">i</span> <span class="special">&lt;</span> <span class="number">10000</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span><span class="special">)</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="char">'.'</span><span class="special">;</span>
<span class="special">}</span>
<span class="special">};</span>
<span class="keyword">int</span> <span class="identifier">main</span><span class="special">(</span><span class="keyword">void</span><span class="special">)</span> <span class="special">{</span>
<span class="identifier">n</span> <span class="identifier">x</span><span class="special">(-</span><span class="number">1</span><span class="special">);</span>
<span class="keyword">auto</span> <span class="identifier">f</span> <span class="special">=</span> <span class="special">[</span><span class="identifier">x</span><span class="special">]()</span> <span class="special">{</span> <span class="comment">// Problem: Expensive copy, but if bind</span>
<span class="identifier">assert</span><span class="special">(</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">i</span> <span class="special">==</span> <span class="special">-</span><span class="number">1</span><span class="special">);</span> <span class="comment">// by `&amp;x` then `x` is not constant.</span>
<span class="special">};</span>
<span class="identifier">f</span><span class="special">();</span>
<span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
<span class="special">}</span>
</pre>
<p>
</p>
</td>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">struct</span> <span class="identifier">n</span> <span class="special">{</span>
<span class="keyword">int</span> <span class="identifier">i</span><span class="special">;</span>
<span class="identifier">n</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">_i</span><span class="special">):</span> <span class="identifier">i</span><span class="special">(</span><span class="identifier">_i</span><span class="special">)</span> <span class="special">{}</span>
<span class="identifier">n</span><span class="special">(</span><span class="identifier">n</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">):</span> <span class="identifier">i</span><span class="special">(</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">i</span><span class="special">)</span> <span class="special">{</span> <span class="comment">// Some time consuming copy operation.</span>
<span class="keyword">for</span> <span class="special">(</span><span class="keyword">unsigned</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> <span class="identifier">i</span> <span class="special">&lt;</span> <span class="number">10000</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span><span class="special">)</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="char">'.'</span><span class="special">;</span>
<span class="special">}</span>
<span class="special">};</span>
<span class="identifier">BOOST_TYPEOF_REGISTER_TYPE</span><span class="special">(</span><span class="identifier">n</span><span class="special">)</span> <span class="comment">// Register for `bind&amp; x` below.</span>
<span class="keyword">int</span> <span class="identifier">main</span><span class="special">(</span><span class="keyword">void</span><span class="special">)</span> <span class="special">{</span>
<span class="identifier">n</span> <span class="identifier">x</span><span class="special">(-</span><span class="number">1</span><span class="special">);</span>
<span class="keyword">void</span> <span class="identifier">BOOST_LOCAL_FUNCTION</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">bind</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">)</span> <span class="special">{</span> <span class="comment">// OK: No copy expensive</span>
<span class="identifier">assert</span><span class="special">(</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">i</span> <span class="special">==</span> <span class="special">-</span><span class="number">1</span><span class="special">);</span> <span class="comment">// copy but constant.</span>
<span class="special">}</span> <span class="identifier">BOOST_LOCAL_FUNCTION_NAME</span><span class="special">(</span><span class="identifier">f</span><span class="special">)</span>
<span class="identifier">f</span><span class="special">();</span>
<span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
<span class="special">}</span>
</pre>
<p>
</p>
</td>
</tr></tbody>
</table></div>
<p>
When constant binding functionality is needed for <a href="http://en.wikipedia.org/wiki/C%2B%2B0x#Lambda_functions_and_expressions" target="_top">C++11
lambda functions</a>, the best alternative might be to bind an extra local
variable declared constant and initialized to the original variable (for example,
see <span class="emphasis"><em>constant blocks</em></span> implemented with <a href="http://en.wikipedia.org/wiki/C%2B%2B0x#Lambda_functions_and_expressions" target="_top">C++11
lambda functions</a> in the <a class="link" href="examples.html" title="Examples">Examples</a>
section).
</p>
<p>
<span class="bold"><strong>Local Functor</strong></span>
</p>
<p>
The following example compares local functions with C++ local functors (see
also <a href="../../../example/add_local_functor.cpp" target="_top"><code class="literal">add_local_functor.cpp</code></a>
and <a href="../../../test/add.cpp" target="_top"><code class="literal">add.cpp</code></a>):
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Local Functor
</p>
</th>
<th>
<p>
Boost.LocalFunction
</p>
</th>
</tr></thead>
<tbody><tr>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">int</span> <span class="identifier">main</span><span class="special">(</span><span class="keyword">void</span><span class="special">)</span> <span class="special">{</span>
<span class="keyword">int</span> <span class="identifier">sum</span> <span class="special">=</span> <span class="number">0</span><span class="special">,</span> <span class="identifier">factor</span> <span class="special">=</span> <span class="number">10</span><span class="special">;</span>
<span class="keyword">struct</span> <span class="identifier">local_add</span> <span class="special">{</span> <span class="comment">// Unfortunately, boilerplate code to program the class.</span>
<span class="identifier">local_add</span><span class="special">(</span><span class="keyword">int</span><span class="special">&amp;</span> <span class="identifier">_sum</span><span class="special">,</span> <span class="keyword">int</span> <span class="identifier">_factor</span><span class="special">):</span> <span class="identifier">sum</span><span class="special">(</span><span class="identifier">_sum</span><span class="special">),</span> <span class="identifier">factor</span><span class="special">(</span><span class="identifier">_factor</span><span class="special">)</span> <span class="special">{}</span>
<span class="keyword">inline</span> <span class="keyword">void</span> <span class="keyword">operator</span><span class="special">()(</span><span class="keyword">int</span> <span class="identifier">num</span><span class="special">)</span> <span class="special">{</span> <span class="comment">// Body uses C++ statement syntax.</span>
<span class="identifier">sum</span> <span class="special">+=</span> <span class="identifier">factor</span> <span class="special">*</span> <span class="identifier">num</span><span class="special">;</span>
<span class="special">}</span>
<span class="keyword">private</span><span class="special">:</span> <span class="comment">// Unfortunately, cannot bind so repeat variable types.</span>
<span class="keyword">int</span><span class="special">&amp;</span> <span class="identifier">sum</span><span class="special">;</span> <span class="comment">// Access `sum` by reference.</span>
<span class="keyword">const</span> <span class="keyword">int</span> <span class="identifier">factor</span><span class="special">;</span> <span class="comment">// Make `factor` constant.</span>
<span class="special">}</span> <span class="identifier">add</span><span class="special">(</span><span class="identifier">sum</span><span class="special">,</span> <span class="identifier">factor</span><span class="special">);</span>
<span class="identifier">add</span><span class="special">(</span><span class="number">1</span><span class="special">);</span>
<span class="keyword">int</span> <span class="identifier">nums</span><span class="special">[]</span> <span class="special">=</span> <span class="special">{</span><span class="number">2</span><span class="special">,</span> <span class="number">3</span><span class="special">};</span>
<span class="comment">// Unfortunately, cannot pass as template parameter to `std::for_each`.</span>
<span class="keyword">for</span><span class="special">(</span><span class="identifier">size_t</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> <span class="identifier">i</span> <span class="special">&lt;</span> <span class="number">2</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span><span class="special">)</span> <span class="identifier">add</span><span class="special">(</span><span class="identifier">nums</span><span class="special">[</span><span class="identifier">i</span><span class="special">]);</span>
<span class="identifier">BOOST_TEST</span><span class="special">(</span><span class="identifier">sum</span> <span class="special">==</span> <span class="number">60</span><span class="special">);</span>
<span class="keyword">return</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">report_errors</span><span class="special">();</span>
<span class="special">}</span>
</pre>
<p>
</p>
</td>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">int</span> <span class="identifier">main</span><span class="special">(</span><span class="keyword">void</span><span class="special">)</span> <span class="special">{</span> <span class="comment">// Some local scope.</span>
<span class="keyword">int</span> <span class="identifier">sum</span> <span class="special">=</span> <span class="number">0</span><span class="special">,</span> <span class="identifier">factor</span> <span class="special">=</span> <span class="number">10</span><span class="special">;</span> <span class="comment">// Variables in scope to bind.</span>
<span class="keyword">void</span> <span class="identifier">BOOST_LOCAL_FUNCTION</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">bind</span> <span class="identifier">factor</span><span class="special">,</span> <span class="identifier">bind</span><span class="special">&amp;</span> <span class="identifier">sum</span><span class="special">,</span> <span class="keyword">int</span> <span class="identifier">num</span><span class="special">)</span> <span class="special">{</span>
<span class="identifier">sum</span> <span class="special">+=</span> <span class="identifier">factor</span> <span class="special">*</span> <span class="identifier">num</span><span class="special">;</span>
<span class="special">}</span> <span class="identifier">BOOST_LOCAL_FUNCTION_NAME</span><span class="special">(</span><span class="identifier">add</span><span class="special">)</span>
<span class="identifier">add</span><span class="special">(</span><span class="number">1</span><span class="special">);</span> <span class="comment">// Call the local function.</span>
<span class="keyword">int</span> <span class="identifier">nums</span><span class="special">[]</span> <span class="special">=</span> <span class="special">{</span><span class="number">2</span><span class="special">,</span> <span class="number">3</span><span class="special">};</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">for_each</span><span class="special">(</span><span class="identifier">nums</span><span class="special">,</span> <span class="identifier">nums</span> <span class="special">+</span> <span class="number">2</span><span class="special">,</span> <span class="identifier">add</span><span class="special">);</span> <span class="comment">// Pass it to an algorithm.</span>
<span class="identifier">BOOST_TEST</span><span class="special">(</span><span class="identifier">sum</span> <span class="special">==</span> <span class="number">60</span><span class="special">);</span> <span class="comment">// Assert final summation value.</span>
<span class="keyword">return</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">report_errors</span><span class="special">();</span>
<span class="special">}</span>
</pre>
<p>
</p>
</td>
</tr></tbody>
</table></div>
<p>
<span class="bold"><strong>Global Functor</strong></span>
</p>
<p>
The following example compares local functions with C++ global functors (see
also <a href="../../../example/add_global_functor.cpp" target="_top"><code class="literal">add_global_functor.cpp</code></a>
and <a href="../../../test/add.cpp" target="_top"><code class="literal">add.cpp</code></a>):
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Global Functor
</p>
</th>
<th>
<p>
Boost.LocalFunction
</p>
</th>
</tr></thead>
<tbody><tr>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="comment">// Unfortunately, cannot be defined locally (so not a real alternative).</span>
<span class="keyword">struct</span> <span class="identifier">global_add</span> <span class="special">{</span> <span class="comment">// Unfortunately, boilerplate code to program the class.</span>
<span class="identifier">global_add</span><span class="special">(</span><span class="keyword">int</span><span class="special">&amp;</span> <span class="identifier">_sum</span><span class="special">,</span> <span class="keyword">int</span> <span class="identifier">_factor</span><span class="special">):</span> <span class="identifier">sum</span><span class="special">(</span><span class="identifier">_sum</span><span class="special">),</span> <span class="identifier">factor</span><span class="special">(</span><span class="identifier">_factor</span><span class="special">)</span> <span class="special">{}</span>
<span class="keyword">inline</span> <span class="keyword">void</span> <span class="keyword">operator</span><span class="special">()(</span><span class="keyword">int</span> <span class="identifier">num</span><span class="special">)</span> <span class="special">{</span> <span class="comment">// Body uses C++ statement syntax.</span>
<span class="identifier">sum</span> <span class="special">+=</span> <span class="identifier">factor</span> <span class="special">*</span> <span class="identifier">num</span><span class="special">;</span>
<span class="special">}</span>
<span class="keyword">private</span><span class="special">:</span> <span class="comment">// Unfortunately, cannot bind so repeat variable types.</span>
<span class="keyword">int</span><span class="special">&amp;</span> <span class="identifier">sum</span><span class="special">;</span> <span class="comment">// Access `sum` by reference.</span>
<span class="keyword">const</span> <span class="keyword">int</span> <span class="identifier">factor</span><span class="special">;</span> <span class="comment">// Make `factor` constant.</span>
<span class="special">};</span>
<span class="keyword">int</span> <span class="identifier">main</span><span class="special">(</span><span class="keyword">void</span><span class="special">)</span> <span class="special">{</span>
<span class="keyword">int</span> <span class="identifier">sum</span> <span class="special">=</span> <span class="number">0</span><span class="special">,</span> <span class="identifier">factor</span> <span class="special">=</span> <span class="number">10</span><span class="special">;</span>
<span class="identifier">global_add</span> <span class="identifier">add</span><span class="special">(</span><span class="identifier">sum</span><span class="special">,</span> <span class="identifier">factor</span><span class="special">);</span>
<span class="identifier">add</span><span class="special">(</span><span class="number">1</span><span class="special">);</span>
<span class="keyword">int</span> <span class="identifier">nums</span><span class="special">[]</span> <span class="special">=</span> <span class="special">{</span><span class="number">2</span><span class="special">,</span> <span class="number">3</span><span class="special">};</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">for_each</span><span class="special">(</span><span class="identifier">nums</span><span class="special">,</span> <span class="identifier">nums</span> <span class="special">+</span> <span class="number">2</span><span class="special">,</span> <span class="identifier">add</span><span class="special">);</span> <span class="comment">// Passed as template parameter.</span>
<span class="identifier">BOOST_TEST</span><span class="special">(</span><span class="identifier">sum</span> <span class="special">==</span> <span class="number">60</span><span class="special">);</span>
<span class="keyword">return</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">report_errors</span><span class="special">();</span>
<span class="special">}</span>
</pre>
<p>
</p>
</td>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">int</span> <span class="identifier">main</span><span class="special">(</span><span class="keyword">void</span><span class="special">)</span> <span class="special">{</span> <span class="comment">// Some local scope.</span>
<span class="keyword">int</span> <span class="identifier">sum</span> <span class="special">=</span> <span class="number">0</span><span class="special">,</span> <span class="identifier">factor</span> <span class="special">=</span> <span class="number">10</span><span class="special">;</span> <span class="comment">// Variables in scope to bind.</span>
<span class="keyword">void</span> <span class="identifier">BOOST_LOCAL_FUNCTION</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">bind</span> <span class="identifier">factor</span><span class="special">,</span> <span class="identifier">bind</span><span class="special">&amp;</span> <span class="identifier">sum</span><span class="special">,</span> <span class="keyword">int</span> <span class="identifier">num</span><span class="special">)</span> <span class="special">{</span>
<span class="identifier">sum</span> <span class="special">+=</span> <span class="identifier">factor</span> <span class="special">*</span> <span class="identifier">num</span><span class="special">;</span>
<span class="special">}</span> <span class="identifier">BOOST_LOCAL_FUNCTION_NAME</span><span class="special">(</span><span class="identifier">add</span><span class="special">)</span>
<span class="identifier">add</span><span class="special">(</span><span class="number">1</span><span class="special">);</span> <span class="comment">// Call the local function.</span>
<span class="keyword">int</span> <span class="identifier">nums</span><span class="special">[]</span> <span class="special">=</span> <span class="special">{</span><span class="number">2</span><span class="special">,</span> <span class="number">3</span><span class="special">};</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">for_each</span><span class="special">(</span><span class="identifier">nums</span><span class="special">,</span> <span class="identifier">nums</span> <span class="special">+</span> <span class="number">2</span><span class="special">,</span> <span class="identifier">add</span><span class="special">);</span> <span class="comment">// Pass it to an algorithm.</span>
<span class="identifier">BOOST_TEST</span><span class="special">(</span><span class="identifier">sum</span> <span class="special">==</span> <span class="number">60</span><span class="special">);</span> <span class="comment">// Assert final summation value.</span>
<span class="keyword">return</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">report_errors</span><span class="special">();</span>
<span class="special">}</span>
</pre>
<p>
</p>
</td>
</tr></tbody>
</table></div>
<p>
However, note that global functors do not allow to define the function locally
so they are not a real alternative implementation of local functions.
</p>
<p>
<span class="bold"><strong>Boost.Phoenix</strong></span>
</p>
<p>
The following example compares local functions with <a href="http://www.boost.org/libs/phoenix" target="_top">Boost.Phoenix</a>
(see also <a href="../../../example/add_phoenix.cpp" target="_top"><code class="literal">add_phoenix.cpp</code></a>
and <a href="../../../test/add.cpp" target="_top"><code class="literal">add.cpp</code></a>):
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Boost.Phoenix
</p>
</th>
<th>
<p>
Boost.LocalFunction
</p>
</th>
</tr></thead>
<tbody><tr>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">int</span> <span class="identifier">main</span><span class="special">(</span><span class="keyword">void</span><span class="special">)</span> <span class="special">{</span>
<span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">phoenix</span><span class="special">::</span><span class="identifier">let</span><span class="special">;</span>
<span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">phoenix</span><span class="special">::</span><span class="identifier">local_names</span><span class="special">::</span><span class="identifier">_f</span><span class="special">;</span>
<span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">phoenix</span><span class="special">::</span><span class="identifier">cref</span><span class="special">;</span>
<span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">phoenix</span><span class="special">::</span><span class="identifier">ref</span><span class="special">;</span>
<span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">phoenix</span><span class="special">::</span><span class="identifier">arg_names</span><span class="special">::</span><span class="identifier">_1</span><span class="special">;</span>
<span class="keyword">int</span> <span class="identifier">sum</span> <span class="special">=</span> <span class="number">0</span><span class="special">,</span> <span class="identifier">factor</span> <span class="special">=</span> <span class="number">10</span><span class="special">;</span>
<span class="keyword">int</span> <span class="identifier">nums</span><span class="special">[]</span> <span class="special">=</span> <span class="special">{</span><span class="number">1</span><span class="special">,</span> <span class="number">2</span><span class="special">,</span> <span class="number">3</span><span class="special">};</span>
<span class="comment">// Passed to template, `factor` by constant, and defined in expression.</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">for_each</span><span class="special">(</span><span class="identifier">nums</span><span class="special">,</span> <span class="identifier">nums</span> <span class="special">+</span> <span class="number">3</span><span class="special">,</span> <span class="identifier">let</span><span class="special">(</span><span class="identifier">_f</span> <span class="special">=</span> <span class="identifier">cref</span><span class="special">(</span><span class="identifier">factor</span><span class="special">))[</span>
<span class="comment">// Unfortunately, body cannot use C++ statement syntax.</span>
<span class="identifier">ref</span><span class="special">(</span><span class="identifier">sum</span><span class="special">)</span> <span class="special">+=</span> <span class="identifier">_f</span> <span class="special">*</span> <span class="identifier">_1</span><span class="special">,</span> <span class="identifier">_1</span> <span class="comment">// Access `sum` by reference.</span>
<span class="special">]);</span>
<span class="identifier">BOOST_TEST</span><span class="special">(</span><span class="identifier">sum</span> <span class="special">==</span> <span class="number">60</span><span class="special">);</span>
<span class="keyword">return</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">report_errors</span><span class="special">();</span>
<span class="special">}</span>
</pre>
<p>
</p>
</td>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">int</span> <span class="identifier">main</span><span class="special">(</span><span class="keyword">void</span><span class="special">)</span> <span class="special">{</span> <span class="comment">// Some local scope.</span>
<span class="keyword">int</span> <span class="identifier">sum</span> <span class="special">=</span> <span class="number">0</span><span class="special">,</span> <span class="identifier">factor</span> <span class="special">=</span> <span class="number">10</span><span class="special">;</span> <span class="comment">// Variables in scope to bind.</span>
<span class="keyword">void</span> <span class="identifier">BOOST_LOCAL_FUNCTION</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">bind</span> <span class="identifier">factor</span><span class="special">,</span> <span class="identifier">bind</span><span class="special">&amp;</span> <span class="identifier">sum</span><span class="special">,</span> <span class="keyword">int</span> <span class="identifier">num</span><span class="special">)</span> <span class="special">{</span>
<span class="identifier">sum</span> <span class="special">+=</span> <span class="identifier">factor</span> <span class="special">*</span> <span class="identifier">num</span><span class="special">;</span>
<span class="special">}</span> <span class="identifier">BOOST_LOCAL_FUNCTION_NAME</span><span class="special">(</span><span class="identifier">add</span><span class="special">)</span>
<span class="identifier">add</span><span class="special">(</span><span class="number">1</span><span class="special">);</span> <span class="comment">// Call the local function.</span>
<span class="keyword">int</span> <span class="identifier">nums</span><span class="special">[]</span> <span class="special">=</span> <span class="special">{</span><span class="number">2</span><span class="special">,</span> <span class="number">3</span><span class="special">};</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">for_each</span><span class="special">(</span><span class="identifier">nums</span><span class="special">,</span> <span class="identifier">nums</span> <span class="special">+</span> <span class="number">2</span><span class="special">,</span> <span class="identifier">add</span><span class="special">);</span> <span class="comment">// Pass it to an algorithm.</span>
<span class="identifier">BOOST_TEST</span><span class="special">(</span><span class="identifier">sum</span> <span class="special">==</span> <span class="number">60</span><span class="special">);</span> <span class="comment">// Assert final summation value.</span>
<span class="keyword">return</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">report_errors</span><span class="special">();</span>
<span class="special">}</span>
</pre>
<p>
</p>
</td>
</tr></tbody>
</table></div>
<p>
The comparison in this section does not include the <a href="http://www.boost.org/libs/lambda" target="_top">Boost.Lambda</a>
library because that library is obsolete and it was replaced by <a href="http://www.boost.org/libs/phoenix" target="_top">Boost.Phoenix</a>.
The <a href="http://www.boost.org/libs/phoenix" target="_top">Boost.Phoenix</a> library
version 3.0 is used for this comparison.
</p>
<h4>
<a name="boost_localfunction.alternatives.h1"></a>
<span class="phrase"><a name="boost_localfunction.alternatives.performances"></a></span><a class="link" href="alternatives.html#boost_localfunction.alternatives.performances">Performances</a>
</h4>
<p>
The following tables compare run-times, compile-times, and binary sizes for
the different alternatives to local functions presented in this section.
</p>
<p>
Overall, this library has compile-times and generates binary sizes similar
to the ones of the other approaches. This library run-times on <a href="http://www.open-std.org/JTC1/SC22/WG21/docs/standards" target="_top">C++03</a>
compilers were measured to be larger than other approaches when compiler optimization
is enabled (using <code class="computeroutput"><span class="identifier">bjam</span> <span class="identifier">release</span>
<span class="special">...</span></code>). However, on compilers that allow
to pass local types as template parameters (e.g., MSVC 8.0 or GCC 4.5.3 with
<a href="http://www.open-std.org/JTC1/SC22/WG21/" target="_top">C++11</a> features
enabled <code class="literal">-std=c++0x</code>, see also <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2657.htm" target="_top">[N2657]</a>
and <a href="http://www.boost.org/libs/chrono" target="_top">Boost.Config</a>'s <code class="computeroutput"><span class="identifier">BOOST_NO_CXX11_LOCAL_CLASS_TEMPLATE_PARAMETERS</span></code>)
this library automatically generates optimized code that runs as fast as the
fastest of the other approaches (see the "Boost.LocalFunction" approach
below). When this library local function is specified <code class="computeroutput"><span class="keyword">inline</span></code>
(see the "Boost.LocalFunction Inline" approach below and the <a class="link" href="advanced_topics.html" title="Advanced Topics">Advanced Topics</a> section)
its run-times are always comparable to both the "Local Functor" and
"Global Functor" approaches. However, in these cases the local function
cannot be portably passed as template parameter (see <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2657.htm" target="_top">[N2657]</a>
and <a href="http://www.boost.org/libs/chrono" target="_top">Boost.Config</a>'s <code class="computeroutput"><span class="identifier">BOOST_NO_CXX11_LOCAL_CLASS_TEMPLATE_PARAMETERS</span></code>)
so <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">for_each</span></code> is replaced by a for-loop (on MSVC
the for-loop, and not the local function in fact the same applies to local
functors, was measured to have worst performances than using <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">for_each</span></code>).
Finally, this library run-times are always among the fastest when no compiler
optimization is enabled (using <code class="computeroutput"><span class="identifier">bjam</span>
<span class="identifier">debug</span> <span class="special">...</span></code>).
</p>
<div class="note"><table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../doc/src/images/note.png"></td>
<th align="left">Note</th>
</tr>
<tr><td align="left" valign="top"><p>
The run-time performances of this library local functions are explained because
on <a href="http://www.open-std.org/JTC1/SC22/WG21/docs/standards" target="_top">C++03</a>
compliant compilers (e.g., GCC 4.5.3 without <code class="literal">-std=c++0x</code>)
this library needs to use a function pointer in order to portably pass the
local function class as a template parameter (see <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2657.htm" target="_top">[N2657]</a>
and the <a class="link" href="implementation.html" title="Annex: Implementation">Implementation</a>
section). For all tested compilers, this function pointer prevents the compiler
optimization algorithms from inlining the local function calls. Instead,
the functors used by other approaches (e.g., <a href="http://www.boost.org/libs/phoenix" target="_top">Boost.Phoenix</a>)
have been observed to allow all tested compilers to inline all the function
calls for optimization. This run-time performance cost is not present on
compilers that allow to pass local types as template parameters (e.g., MSVC
8.0 or GCC 4.5.3 with <a href="http://www.open-std.org/JTC1/SC22/WG21/" target="_top">C++11</a>
features enabled <code class="literal">-std=c++0x</code>, see <a href="http://www.boost.org/libs/chrono" target="_top">Boost.Config</a>'s
<code class="computeroutput"><span class="identifier">BOOST_NO_CXX11_LOCAL_CLASS_TEMPLATE_PARAMETERS</span></code>)
because this library does not have to use the extra function pointer to implement
the local function call (it directly passes the local class type as template
parameter).
</p></td></tr>
</table></div>
<p>
This run-time performance cost on <a href="http://www.open-std.org/JTC1/SC22/WG21/docs/standards" target="_top">C++03</a>
compilers might or might not be an issue depending on the performance requirements
of specific applications. For example, an application might already be using
a number of indirect function calls (function pointers, virtual functions,
etc) for which the overhead added by using the one extra function pointer required
by the local function call might not be noticeable within the overall program
run-time.
</p>
<p>
Finally, note that only a very simple local function body with just a single
instruction was used for the anaylsis presented here (see the source files
below). The authors have not studied how this library and the other approaches
will perform with respect to each other when a more complex set of instructions
is programmed for the local function body (e.g., <span class="emphasis"><em>if</em></span> a
more complex set of instructions in the local function body were to inhibit
some compiler from inlining function objects also other approaches like <a href="http://en.wikipedia.org/wiki/C%2B%2B0x#Lambda_functions_and_expressions" target="_top">C++11
lambda functions</a> and <a href="http://www.boost.org/libs/phoenix" target="_top">Boost.Phoenix</a>
<span class="emphasis"><em>could</em></span> start to show higher run-times even when optimization
is enabled).
</p>
<p>
The following commands were executed from the library example directory to
measure compile-time, binary size, and run-time respectively:
</p>
<pre class="programlisting">&gt; touch &lt;FILE_NAME&gt;.cpp # force recompilation
&gt; python chrono.py bjam {release|debug} &lt;FILE_NAME&gt; # compile-time
&gt; size &lt;FILE_NAME&gt; # binary size
&gt; ./&lt;FILE_NAME&gt; # run-time
</pre>
<p>
The local function was called <code class="literal">1e8</code> times to add together
all the elements of a vector and the run-time was measured using <a href="http://www.boost.org/libs/chrono" target="_top">Boost.Chrono</a>
averaging over <code class="literal">10</code> executions of the vector summation (see
the source files below).
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Legend
</p>
</th>
<th>
<p>
Approach
</p>
</th>
<th>
<p>
Source File
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<span class="inlinemediaobject"><img src="../../../example/profile_legend_local_function.png" alt="profile_legend_local_function"></span>
</p>
</td>
<td>
<p>
<a href="http://www.boost.org/libs/local_function" target="_top">Boost.LocalFunction</a>
</p>
</td>
<td>
<p>
<a href="../../../example/profile_local_function.cpp" target="_top"><code class="literal">profile_local_function.cpp</code></a>
</p>
</td>
</tr>
<tr>
<td>
<p>
<span class="inlinemediaobject"><img src="../../../example/profile_legend_local_function_inline.png" alt="profile_legend_local_function_inline"></span>
</p>
</td>
<td>
<p>
<a href="http://www.boost.org/libs/local_function" target="_top">Boost.LocalFunction</a>
inline
</p>
</td>
<td>
<p>
<a href="../../../example/profile_local_function_inline.cpp" target="_top"><code class="literal">profile_local_function_inline.cpp</code></a>
</p>
</td>
</tr>
<tr>
<td>
<p>
<span class="inlinemediaobject"><img src="../../../example/profile_legend_cxx11_lambda.png" alt="profile_legend_cxx11_lambda"></span>
</p>
</td>
<td>
<p>
<a href="http://www.open-std.org/JTC1/SC22/WG21/" target="_top">C++11</a>
Lambda Function <a href="#ftn.boost_localfunction.alternatives.f0" class="footnote" name="boost_localfunction.alternatives.f0"><sup class="footnote">[a]</sup></a>
</p>
</td>
<td>
<p>
<a href="../../../example/profile_cxx11_lambda.cpp" target="_top"><code class="literal">profile_cxx11_lambda.cpp</code></a>
</p>
</td>
</tr>
<tr>
<td>
<p>
<span class="inlinemediaobject"><img src="../../../example/profile_legend_local_functor.png" alt="profile_legend_local_functor"></span>
</p>
</td>
<td>
<p>
Local Functor
</p>
</td>
<td>
<p>
<a href="../../../example/profile_local_functor.cpp" target="_top"><code class="literal">profile_local_functor.cpp</code></a>
</p>
</td>
</tr>
<tr>
<td>
<p>
<span class="inlinemediaobject"><img src="../../../example/profile_legend_global_functor.png" alt="profile_legend_global_functor"></span>
</p>
</td>
<td>
<p>
Global Functor
</p>
</td>
<td>
<p>
<a href="../../../example/profile_global_functor.cpp" target="_top"><code class="literal">profile_global_functor.cpp</code></a>
</p>
</td>
</tr>
<tr>
<td>
<p>
<span class="inlinemediaobject"><img src="../../../example/profile_legend_phoenix.png" alt="profile_legend_phoenix"></span>
</p>
</td>
<td>
<p>
<a href="http://www.boost.org/libs/phoenix" target="_top">Boost.Phoenix</a>
</p>
</td>
<td>
<p>
<a href="../../../example/profile_phoenix.cpp" target="_top"><code class="literal">profile_phoenix.cpp</code></a>
</p>
</td>
</tr>
</tbody>
<tbody class="footnotes"><tr><td colspan="3"><div id="ftn.boost_localfunction.alternatives.f0" class="footnote"><p><a href="#boost_localfunction.alternatives.f0" class="para"><sup class="para">[a] </sup></a>
Measurements available only for <a href="http://www.open-std.org/JTC1/SC22/WG21/" target="_top">C++11</a>
compilers.
</p></div></td></tr></tbody>
</table></div>
<div class="informaltable"><table class="table">
<colgroup><col></colgroup>
<thead><tr><th>
<p>
GCC 4.5.3 With C++11 Lambda Functions and "Local Classes as
Template Parameters" (<code class="literal">bjam cxxflags=-std=c++0x ...</code>)
</p>
</th></tr></thead>
<tbody>
<tr><td>
<p>
<span class="bold"><strong>Compiled with <code class="literal">bjam release ...</code>
for maximum optimization (<code class="literal">-O3 -finline-functions</code>)</strong></span>
<span class="inlinemediaobject"><img src="../../../example/profile_gcc_cxx11_release.png" width="1170" alt="profile_gcc_cxx11_release"></span>
</p>
</td></tr>
<tr><td>
<p>
<span class="bold"><strong>Compiled with <code class="literal">bjam debug ...</code>
for no optimization (<code class="literal">-O0 -fno-inline</code>)</strong></span>
<span class="inlinemediaobject"><img src="../../../example/profile_gcc_cxx11_debug.png" width="1170" alt="profile_gcc_cxx11_debug"></span>
</p>
</td></tr>
</tbody>
</table></div>
<div class="informaltable"><table class="table">
<colgroup><col></colgroup>
<thead><tr><th>
<p>
MSVC 8.0 With "Local Classes as Template Parameters" (Without
C++11 Lambda Functions)
</p>
</th></tr></thead>
<tbody>
<tr><td>
<p>
<span class="bold"><strong>Compiled with <code class="literal">bjam release ...</code>
for maximum optimization (<code class="literal">/O2 /Ob2</code>)</strong></span>
<span class="inlinemediaobject"><img src="../../../example/profile_msvc_release.png" width="1170" alt="profile_msvc_release"></span>
</p>
</td></tr>
<tr><td>
<p>
<span class="bold"><strong>Compiled with <code class="literal">bjam debug ...</code>
for no optimization (<code class="literal">/Od /Ob0</code>)</strong></span> <span class="inlinemediaobject"><img src="../../../example/profile_msvc_debug.png" width="1170" alt="profile_msvc_debug"></span>
</p>
</td></tr>
</tbody>
</table></div>
<div class="informaltable"><table class="table">
<colgroup><col></colgroup>
<thead><tr><th>
<p>
GCC 4.3.4 With <a href="http://www.open-std.org/JTC1/SC22/WG21/docs/standards" target="_top">C++03</a>
Only (Without <a href="http://www.open-std.org/JTC1/SC22/WG21/" target="_top">C++11</a>
Lambda Functions and Without "Local Classes as Template Parameters")
</p>
</th></tr></thead>
<tbody>
<tr><td>
<p>
<span class="bold"><strong>Compiled with <code class="literal">bjam release ...</code>
for maximum optimization (<code class="literal">-O3 -finline-functions</code>)</strong></span>
<span class="inlinemediaobject"><img src="../../../example/profile_gcc_release.png" width="1170" alt="profile_gcc_release"></span>
</p>
</td></tr>
<tr><td>
<p>
<span class="bold"><strong>Compiled with <code class="literal">bjam debug ...</code>
for no optimization (<code class="literal">-O0 -fno-inline</code>)</strong></span>
<span class="inlinemediaobject"><img src="../../../example/profile_gcc_debug.png" width="1170" alt="profile_gcc_debug"></span>
</p>
</td></tr>
</tbody>
</table></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 &#169; 2009-2012 Lorenzo
Caminiti<p>
Distributed under the Boost Software License, Version 1.0 (see accompanying
file LICENSE_1_0.txt or a 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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