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| 25 | <div class="section"> | |
| 26 | <div class="titlepage"><div><div><h3 class="title"> | |
| 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"><</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">></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"><</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">></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> | |
| 69 | </div> | |
| 70 | <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> | |
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| 72 | <td align="right"><div class="copyright-footer">Copyright © 2006-2010, 2012-2014 Nikhar Agrawal, | |
| 73 | Anton Bikineev, Paul A. Bristow, Marco Guazzone, Christopher Kormanyos, Hubert | |
| 74 | Holin, Bruno Lalande, John Maddock, Jeremy Murphy, Johan Råde, Gautam Sewani, | |
| 75 | Benjamin Sobotta, 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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