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71 lines
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<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Lazy Construction and Conversions</b></font>
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<a name="lazy_c___casts"></a><h2>Lazy C++ Casts</h2><p>
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The set of lazy C++ cast template classes and functions provide a way of lazily casting certain type to another during parsing. The lazy C++ templates are (syntactically) used very much like the well known C++ casts:</p>
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<code><pre>
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<span class=identifier>A </span><span class=special>*</span><span class=identifier>a </span><span class=special>= </span><span class=identifier>static_cast_</span><span class=special><</span><span class=identifier>A </span><span class=special>*>(</span><span class=identifier>_a_lambda_expression_</span><span class=special>);
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</span></pre></code>
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<p>
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These casts parallel the ones in the C++ language. Take note however that the <i>lazy</i> versions have a trailing underscore.</p>
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<ul><li>static_cast_<T>(lambda_expression)</li><li>dynamic_cast_<T>(lambda_expression)</li><li>const_cast_<T>(lambda_expression)</li><li>reinterpret_cast_<T>(lambda_expression)</li></ul><table width="80%" border="0" align="center">
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<td class="note_box">
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<img src="theme/note.gif"></img> <b>Acknowledgement:</b><br><br><b>Hartmut Kaiser</b> implemented the lazy casts and constructors based on his original work on <a href="http://spirit.sourceforge.net">
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Spirit</a> SE "semantic expressions" (the precursor of Phoenix). </td>
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<a name="lazy_object_construction"></a><h2>Lazy object construction</h2><p>
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A set of lazy constructor template classes and functions provide a way of lazily constructing an object of a type from an arbitrary set of lazy arguments in the form of lambda expressions. The construct_ templates are (syntactically) used very much like the well known C++ casts:</p>
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<code><pre>
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<span class=identifier>A </span><span class=identifier>a </span><span class=special>= </span><span class=identifier>construct_</span><span class=special><</span><span class=identifier>A</span><span class=special>>(</span><span class=identifier>lambda_arg1</span><span class=special>, </span><span class=identifier>lambda_arg2</span><span class=special>, ..., </span><span class=identifier>lambda_argN</span><span class=special>);
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</span></pre></code>
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<p>
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where the given parameters are become the parameters to the contructor of the object of type A. (This implies, that type A is expected to have a constructor with a corresponsing set of parameter types.)</p>
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<img src="theme/bulb.gif"></img> The ultimate maximum number of actual parameters is limited by the preprocessor constant PHOENIX_CONSTRUCT_LIMIT. Note though, that this limit should not be greater than PHOENIX_LIMIT. </td>
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<p class="copyright">Copyright © 2001-2002 Joel de Guzman<br>
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<br>
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<font size="2">Use, modification and distribution is subject to the Boost Software
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License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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http://www.boost.org/LICENSE_1_0.txt) </font> </p>
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