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| 13 | <table cellpadding="2" width="100%"><tr> | |
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| 24 | </div> | |
| 25 | <div class="section"> | |
| 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"><<</span> <span class="identifier">arg1</span> <span class="special"><<</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> | |
| 100 | </div> | |
| 101 | <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> | |
| 102 | <td align="left"></td> | |
| 103 | <td align="right"><div class="copyright-footer">Copyright © 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>) | |
| 107 | </p> | |
| 108 | </div></td> | |
| 109 | </tr></table> | |
| 110 | <hr> | |
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| 113 | </div> | |
| 114 | </body> | |
| 115 | </html> |