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  26 <div class="titlepage"><div><div><h4 class="title">
  27 <a name="phoenix.modules.statement.for_statement"></a><a class="link" href="for_statement.html" title="for_ Statement">for_ Statement</a>
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  29 <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</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">for</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
  30 </pre>
  31 <p>
  32           The syntax is:
  33         </p>
  34 <pre class="programlisting"><span class="identifier">for_</span><span class="special">(</span><span class="identifier">init_statement</span><span class="special">,</span> <span class="identifier">conditional_expression</span><span class="special">,</span> <span class="identifier">step_statement</span><span class="special">)</span>
  35 <span class="special">[</span>
  36     <span class="identifier">sequenced_statements</span>
  37 <span class="special">]</span>
  38 </pre>
  39 <p>
  40           It is again very similar to the C++ for statement. Take note that the init_statement,
  41           conditional_expression and step_statement are separated by the comma instead of the semi-colon
  42           and each must be present (i.e. <code class="computeroutput"><span class="identifier">for_</span><span class="special">(,,)</span></code> is invalid). This is a case where the
  43           <a class="link" href="../core/nothing.html" title="Nothing"><code class="computeroutput"><span class="identifier">nothing</span></code></a>
  44           actor can be useful.
  45         </p>
  46 <p>
  47           Example: This code prints each element N times where N is the element's
  48           value. A newline terminates the printout of each value.
  49         </p>
  50 <pre class="programlisting"><span class="keyword">int</span> <span class="identifier">iii</span><span class="special">;</span>
  51 <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>
  52     <span class="special">(</span>
  53         <span class="identifier">for_</span><span class="special">(</span><span class="identifier">ref</span><span class="special">(</span><span class="identifier">iii</span><span class="special">)</span> <span class="special">=</span> <span class="number">0</span><span class="special">,</span> <span class="identifier">ref</span><span class="special">(</span><span class="identifier">iii</span><span class="special">)</span> <span class="special">&lt;</span> <span class="identifier">arg1</span><span class="special">,</span> <span class="special">++</span><span class="identifier">ref</span><span class="special">(</span><span class="identifier">iii</span><span class="special">))</span>
  54         <span class="special">[</span>
  55             <span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">arg1</span> <span class="special">&lt;&lt;</span> <span class="string">", "</span>
  56         <span class="special">],</span>
  57         <span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">val</span><span class="special">(</span><span class="string">"\n"</span><span class="special">)</span>
  58     <span class="special">)</span>
  59 <span class="special">);</span>
  60 </pre>
  61 <p>
  62           As before, all these are lazily evaluated. The result of such statements
  63           are in fact expressions that are passed on to STL's for_each function.
  64           In the viewpoint of <code class="computeroutput"><span class="identifier">for_each</span></code>,
  65           what was passed is just a functor, no more, no less.
  66         </p>
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  70 <td align="right"><div class="copyright-footer">Copyright &#169; 2002-2005, 2010, 2014, 2015 Joel de Guzman, Dan Marsden, Thomas
  71       Heller, John Fletcher<p>
  72         Distributed under the Boost Software License, Version 1.0. (See accompanying
  73         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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