ceph/src/boost/libs/phoenix/doc/html/phoenix/modules/statement.html

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  26 <div class="titlepage"><div><div><h3 class="title">
  27 <a name="phoenix.modules.statement"></a><a class="link" href="statement.html" title="Statement">Statement</a>
  28 </h3></div></div></div>
  29 <div class="toc"><dl>
  30 <dt><span class="section"><a href="statement/block_statement.html">Block Statement</a></span></dt>
  31 <dt><span class="section"><a href="statement/if__statement.html">if_ Statement</a></span></dt>
  32 <dt><span class="section"><a href="statement/___if_else_____statement.html">if_else_ Statement</a></span></dt>
  33 <dt><span class="section"><a href="statement/switch__statement.html">switch_
  34         Statement</a></span></dt>
  35 <dt><span class="section"><a href="statement/while__statement.html">while_
  36         Statement</a></span></dt>
  37 <dt><span class="section"><a href="statement/___do_while_____statement.html">do_while_ Statement</a></span></dt>
  38 <dt><span class="section"><a href="statement/for_statement.html">for_ Statement</a></span></dt>
  39 <dt><span class="section"><a href="statement/try__catch__statement.html">try_
  40         catch_ Statement</a></span></dt>
  41 <dt><span class="section"><a href="statement/throw_.html">throw_</a></span></dt>
  42 </dl></div>
  43 <p>
  44         <span class="bold"><strong><span class="emphasis"><em>Lazy statements...</em></span></strong></span>
  45       </p>
  46 <p>
  47         The expressions presented so far are sufficiently powerful to construct quite
  48         elaborate structures. We have presented lazy-functions and lazy-operators.
  49         How about lazy-statements? First, an appetizer:
  50       </p>
  51 <p>
  52         Print all odd-numbered contents of an STL container using <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">for_each</span></code>
  53         (<a href="../../../../example/all_odds.cpp" target="_top">all_odds.cpp</a>):
  54       </p>
  55 <pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">for_each</span><span class="special">(</span><span class="identifier">c</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">c</span><span class="special">.</span><span class="identifier">end</span><span class="special">(),</span>
  56     <span class="identifier">if_</span><span class="special">(</span><span class="identifier">arg1</span> <span class="special">%</span> <span class="number">2</span> <span class="special">==</span> <span class="number">1</span><span class="special">)</span>
  57     <span class="special">[</span>
  58         <span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">arg1</span> <span class="special">&lt;&lt;</span> <span class="char">' '</span>
  59     <span class="special">]</span>
  60 <span class="special">);</span>
  61 </pre>
  62 <p>
  63         Huh? Is that valid C++? Read on...
  64       </p>
  65 <p>
  66         Yes, it is valid C++. The sample code above is as close as you can get to
  67         the syntax of C++. This stylized C++ syntax differs from actual C++ code.
  68         First, the <code class="computeroutput"><span class="keyword">if</span></code> has a trailing
  69         underscore. Second, the block uses square brackets instead of the familiar
  70         curly braces {}.
  71       </p>
  72 <div class="note"><table border="0" summary="Note">
  73 <tr>
  74 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../doc/src/images/note.png"></td>
  75 <th align="left">Note</th>
  76 </tr>
  77 <tr><td align="left" valign="top">
  78 <p>
  79           <span class="bold"><strong>C++ in C++?</strong></span>
  80         </p>
  81 <p>
  82           In as much as <a href="http://spirit.sourceforge.net" target="_top">Spirit</a>
  83           attempts to mimic EBNF in C++, Phoenix attempts to mimic C++ in C++!!!
  84         </p>
  85 </td></tr>
  86 </table></div>
  87 <div class="note"><table border="0" summary="Note">
  88 <tr>
  89 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../doc/src/images/note.png"></td>
  90 <th align="left">Note</th>
  91 </tr>
  92 <tr><td align="left" valign="top"><p>
  93           Unlike lazy functions and lazy operators, lazy statements always return
  94           void.
  95         </p></td></tr>
  96 </table></div>
  97 <p>
  98         Here are more examples with annotations. The code almost speaks for itself.
  99       </p>
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 101 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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 103 <td align="right"><div class="copyright-footer">Copyright &#169; 2002-2005, 2010, 2014, 2015 Joel de Guzman, Dan Marsden, Thomas
 104       Heller, John Fletcher<p>
 105         Distributed under the Boost Software License, Version 1.0. (See accompanying
 106         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>)
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