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  27 <a name="math_toolkit.tutorial.non_templ"></a><a class="link" href="non_templ.html" title="Use in non-template code">Use in non-template
  28       code</a>
  29 </h3></div></div></div>
  30 <p>
  31         When using the math constants at your chosen fixed precision in non-template
  32         code, you can simply add a <code class="computeroutput"><span class="keyword">using</span> <span class="keyword">namespace</span></code> declaration, for example, <code class="computeroutput"><span class="keyword">using</span> <span class="keyword">namespace</span>
  33         <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">double_constants</span></code>, to make the constants
  34         of the correct precision for your code visible in the current scope, and
  35         then use each constant <span class="emphasis"><em>as a simple variable - sans brackets</em></span>:
  36       </p>
  37 <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">math</span><span class="special">/</span><span class="identifier">constants</span><span class="special">/</span><span class="identifier">constants</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
  38
  39 <span class="keyword">double</span> <span class="identifier">area</span><span class="special">(</span><span class="keyword">double</span> <span class="identifier">r</span><span class="special">)</span>
  40 <span class="special">{</span>
  41    <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">double_constants</span><span class="special">;</span>
  42    <span class="keyword">return</span> <span class="identifier">pi</span> <span class="special">*</span> <span class="identifier">r</span> <span class="special">*</span> <span class="identifier">r</span><span class="special">;</span>
  43 <span class="special">}</span>
  44 </pre>
  45 <p>
  46         Had our function been written as taking a <code class="computeroutput"><span class="keyword">float</span></code>
  47         rather than a <code class="computeroutput"><span class="keyword">double</span></code>, we could
  48         have written instead:
  49       </p>
  50 <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">math</span><span class="special">/</span><span class="identifier">constants</span><span class="special">/</span><span class="identifier">constants</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
  51
  52 <span class="keyword">float</span> <span class="identifier">area</span><span class="special">(</span><span class="keyword">float</span> <span class="identifier">r</span><span class="special">)</span>
  53 <span class="special">{</span>
  54    <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">float_constants</span><span class="special">;</span>
  55    <span class="keyword">return</span> <span class="identifier">pi</span> <span class="special">*</span> <span class="identifier">r</span> <span class="special">*</span> <span class="identifier">r</span><span class="special">;</span>
  56 <span class="special">}</span>
  57 </pre>
  58 <p>
  59         Likewise, constants that are suitable for use at <code class="computeroutput"><span class="keyword">long</span>
  60         <span class="keyword">double</span></code> precision are available in
  61         the namespace <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">long_double_constants</span></code>.
  62       </p>
  63 <p>
  64         You can see the full list of available constants at <a class="link" href="../constants.html" title="The Mathematical Constants">math_toolkit.constants</a>.
  65       </p>
  66 <p>
  67         Some examples of using constants are at <a href="../../../../example/constants_eg1.cpp" target="_top">constants_eg1</a>.
  68       </p>
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  72 <td align="right"><div class="copyright-footer">Copyright &#169; 2006-2010, 2012-2014 Nikhar Agrawal,
  73       Anton Bikineev, Paul A. Bristow, Marco Guazzone, Christopher Kormanyos, Hubert
  74       Holin, Bruno Lalande, John Maddock, Johan R&#229;de, Gautam Sewani, Benjamin Sobotta,
  75       Thijs van den Berg, Daryle Walker and Xiaogang Zhang<p>
  76         Distributed under the Boost Software License, Version 1.0. (See accompanying
  77         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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