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| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="phoenix.modules.statement"></a><a class="link" href="statement.html" title="Statement">Statement</a> |
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| <div class="toc"><dl> |
| <dt><span class="section"><a href="statement/block_statement.html">Block Statement</a></span></dt> |
| <dt><span class="section"><a href="statement/if__statement.html">if_ Statement</a></span></dt> |
| <dt><span class="section"><a href="statement/___if_else_____statement.html">if_else_ Statement</a></span></dt> |
| <dt><span class="section"><a href="statement/switch__statement.html">switch_ |
| Statement</a></span></dt> |
| <dt><span class="section"><a href="statement/while__statement.html">while_ |
| Statement</a></span></dt> |
| <dt><span class="section"><a href="statement/___do_while_____statement.html">do_while_ Statement</a></span></dt> |
| <dt><span class="section"><a href="statement/for_statement.html">for_ Statement</a></span></dt> |
| <dt><span class="section"><a href="statement/try__catch__statement.html">try_ |
| catch_ Statement</a></span></dt> |
| <dt><span class="section"><a href="statement/throw_.html">throw_</a></span></dt> |
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| <p> |
| <span class="bold"><strong><span class="emphasis"><em>Lazy statements...</em></span></strong></span> |
| </p> |
| <p> |
| The expressions presented so far are sufficiently powerful to construct quite |
| elaborate structures. We have presented lazy-functions and lazy-operators. |
| How about lazy-statements? First, an appetizer: |
| </p> |
| <p> |
| 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> |
| (<a href="../../../../example/all_odds.cpp" target="_top">all_odds.cpp</a>): |
| </p> |
| <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> |
| <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> |
| <span class="special">[</span> |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">arg1</span> <span class="special"><<</span> <span class="char">' '</span> |
| <span class="special">]</span> |
| <span class="special">);</span> |
| </pre> |
| <p> |
| Huh? Is that valid C++? Read on... |
| </p> |
| <p> |
| Yes, it is valid C++. The sample code above is as close as you can get to |
| the syntax of C++. This stylized C++ syntax differs from actual C++ code. |
| First, the <code class="computeroutput"><span class="keyword">if</span></code> has a trailing |
| underscore. Second, the block uses square brackets instead of the familiar |
| curly braces {}. |
| </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> |
| <span class="bold"><strong>C++ in C++?</strong></span> |
| </p> |
| <p> |
| In as much as <a href="http://spirit.sourceforge.net" target="_top">Spirit</a> |
| attempts to mimic EBNF in C++, Phoenix attempts to mimic C++ in C++!!! |
| </p> |
| </td></tr> |
| </table></div> |
| <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> |
| Unlike lazy functions and lazy operators, lazy statements always return |
| void. |
| </p></td></tr> |
| </table></div> |
| <p> |
| Here are more examples with annotations. The code almost speaks for itself. |
| </p> |
| </div> |
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| <td align="right"><div class="copyright-footer">Copyright © 2002-2005, 2010 Joel de Guzman, Dan Marsden, Thomas Heller<p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| 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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