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| <title>The MPL Reference Manual: protect</title> |
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| <td class="header-group page-location"><a href="../refmanual.html" class="navigation-link">Front Page</a> / <a href="./metafunctions.html" class="navigation-link">Metafunctions</a> / <a href="./composition-and-argument-binding.html" class="navigation-link">Composition and Argument Binding</a> / <a href="./protect.html" class="navigation-link">protect</a></td> |
| </tr></table><div class="header-separator"></div> |
| <div class="section" id="protect"> |
| <h1><a class="toc-backref" href="./composition-and-argument-binding.html#id1534">protect</a></h1> |
| <div class="section" id="id953"> |
| <h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3> |
| <pre class="literal-block"> |
| template< |
| typename F |
| > |
| struct <a href="./protect.html" class="identifier">protect</a> |
| { |
| // <em>unspecified</em> |
| // <em>...</em> |
| }; |
| </pre> |
| </div> |
| <div class="section" id="id954"> |
| <h3><a class="subsection-title" href="#description" name="description">Description</a></h3> |
| <p><tt class="literal"><span class="pre"><a href="./protect.html" class="identifier">protect</a></span></tt> is an identity wrapper for a <a class="reference internal" href="./metafunction-class.html">Metafunction Class</a> that prevents |
| its argument from being recognized as a <a class="reference internal" href="./terminology.html#bind-expression">bind expression</a>.</p> |
| </div> |
| <div class="section" id="id955"> |
| <h3><a class="subsection-title" href="#header" name="header">Header</a></h3> |
| <pre class="literal-block"> |
| #include <<a href="../../../../boost/mpl/protect.hpp" class="header">boost/mpl/protect.hpp</a>> |
| </pre> |
| </div> |
| <div class="section" id="id956"> |
| <h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3> |
| <table border="1" class="docutils table"> |
| <colgroup> |
| <col width="19%" /> |
| <col width="33%" /> |
| <col width="48%" /> |
| </colgroup> |
| <thead valign="bottom"> |
| <tr><th class="head">Parameter</th> |
| <th class="head">Requirement</th> |
| <th class="head">Description</th> |
| </tr> |
| </thead> |
| <tbody valign="top"> |
| <tr><td><tt class="literal"><span class="pre">F</span></tt></td> |
| <td><a class="reference internal" href="./metafunction-class.html">Metafunction Class</a></td> |
| <td>A metafunction class to wrap.</td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <div class="section" id="id957"> |
| <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> |
| <p>For any <a class="reference internal" href="./metafunction-class.html">Metafunction Class</a> <tt class="literal"><span class="pre">f</span></tt>:</p> |
| <pre class="literal-block"> |
| typedef <a href="./protect.html" class="identifier">protect</a><f> g; |
| </pre> |
| <table class="docutils field-list" frame="void" rules="none"> |
| <col class="field-name" /> |
| <col class="field-body" /> |
| <tbody valign="top"> |
| <tr class="field"><th class="field-name">Return type:</th><td class="field-body"><p class="first"><a class="reference internal" href="./metafunction-class.html">Metafunction Class</a>.</p> |
| </td> |
| </tr> |
| <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">If <tt class="literal"><span class="pre">f</span></tt> is a <a class="reference internal" href="./terminology.html#bind-expression">bind expression</a>, equivalent to</p> |
| <pre class="literal-block"> |
| struct g |
| { |
| template< |
| typename U1 = <em>unspecified</em>,<em>...</em> typename U<em>n</em> = <em>unspecified</em> |
| > |
| struct <a href="./apply.html" class="identifier">apply</a> |
| : <a href="./apply-wrap.html" class="identifier">apply_wrap</a><em>n</em><f,U1,<em>...</em>U<em>n</em>> |
| { |
| }; |
| }; |
| </pre> |
| <p class="last">otherwise equivalent to <tt class="literal"><span class="pre">typedef</span> <span class="pre">f</span> <span class="pre">g;</span></tt>.</p> |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <div class="section" id="id958"> |
| <h3><a class="subsection-title" href="#example" name="example">Example</a></h3> |
| <pre class="literal-block"> |
| struct f |
| { |
| template< typename T1, typename T2 > struct <a href="./apply.html" class="identifier">apply</a> |
| { |
| typedef T2 type; |
| }; |
| }; |
| |
| typedef <a href="./bind.html" class="identifier">bind</a>< <a href="./quote.html" class="identifier">quote</a><tt class="literal"><span class="pre">3</span></tt><<a href="./if.html" class="identifier">if_</a>>,<a href="./placeholders.html" class="identifier">_1</a>,<a href="./placeholders.html" class="identifier">_2</a>,<a href="./bind.html" class="identifier">bind</a><f,<a href="./placeholders.html" class="identifier">_1</a>,<a href="./placeholders.html" class="identifier">_2</a>> > b1; |
| typedef <a href="./bind.html" class="identifier">bind</a>< <a href="./quote.html" class="identifier">quote</a><tt class="literal"><span class="pre">3</span></tt><<a href="./if.html" class="identifier">if_</a>>,<a href="./placeholders.html" class="identifier">_1</a>,<a href="./placeholders.html" class="identifier">_2</a>,<a href="./protect.html" class="identifier">protect</a>< <a href="./bind.html" class="identifier">bind</a><f,<a href="./placeholders.html" class="identifier">_1</a>,<a href="./placeholders.html" class="identifier">_2</a>> > > b2; |
| |
| typedef <a href="./apply-wrap.html" class="identifier">apply_wrap</a><tt class="literal"><span class="pre">2</span></tt>< b1,<a href="./bool.html" class="identifier">false_</a>,char >::type r1; |
| typedef <a href="./apply-wrap.html" class="identifier">apply_wrap</a><tt class="literal"><span class="pre">2</span></tt>< b2,<a href="./bool.html" class="identifier">false_</a>,char >::type r2; |
| |
| <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same<r1,char> )); |
| <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same<r2,<a href="./protect.html" class="identifier">protect</a>< <a href="./bind.html" class="identifier">bind</a><f,<a href="./placeholders.html" class="identifier">_1</a>,<a href="./placeholders.html" class="identifier">_2</a>> > > )); |
| </pre> |
| </div> |
| <div class="section" id="id959"> |
| <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3> |
| <p><a class="reference internal" href="./composition-and-argument-binding.html">Composition and Argument Binding</a>, <a class="reference internal" href="./invocation.html">invocation</a>, <a class="reference internal" href="./bind.html">bind</a>, <a class="reference internal" href="./quote.html">quote</a>, <a class="reference internal" href="./apply-wrap.html">apply_wrap</a></p> |
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