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| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="phoenix.modules.statement.___if_else_____statement"></a><a class="link" href="___if_else_____statement.html" title="if_else_ Statement">if_else_ Statement</a> |
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| <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">phoenix</span><span class="special">/</span><span class="identifier">statement</span><span class="special">/</span><span class="keyword">if</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| </pre> |
| <p> |
| The syntax is |
| </p> |
| <pre class="programlisting"><span class="identifier">if_</span><span class="special">(</span><span class="identifier">conditional_expression</span><span class="special">)</span> |
| <span class="special">[</span> |
| <span class="identifier">sequenced_statements</span> |
| <span class="special">]</span> |
| <span class="special">.</span><span class="identifier">else_</span> |
| <span class="special">[</span> |
| <span class="identifier">sequenced_statements</span> |
| <span class="special">]</span> |
| </pre> |
| <p> |
| Take note that <code class="computeroutput"><span class="keyword">else</span></code> has a |
| leading dot and a trailing underscore: <code class="computeroutput"><span class="special">.</span><span class="identifier">else_</span></code> |
| </p> |
| <p> |
| Example: This code prints out all the elements and appends <code class="computeroutput"><span class="string">" > 5"</span></code>, <code class="computeroutput"><span class="string">" |
| == 5"</span></code> or <code class="computeroutput"><span class="string">" < 5"</span></code> |
| depending on the element's actual value: |
| </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">5</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="string">" > 5\n"</span> |
| <span class="special">]</span> |
| <span class="special">.</span><span class="identifier">else_</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">5</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="string">" == 5\n"</span> |
| <span class="special">]</span> |
| <span class="special">.</span><span class="identifier">else_</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="string">" < 5\n"</span> |
| <span class="special">]</span> |
| <span class="special">]</span> |
| <span class="special">);</span> |
| </pre> |
| <p> |
| Notice how the <code class="computeroutput"><span class="identifier">if_else_</span></code> |
| statement is nested. |
| </p> |
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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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