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| <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 |
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| <p> |
| When using the math constants at your chosen fixed precision in non-template |
| 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> |
| <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 |
| of the correct precision for your code visible in the current scope, and |
| then use each constant <span class="emphasis"><em>as a simple variable - sans brackets</em></span>: |
| </p> |
| <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> |
| |
| <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> |
| <span class="special">{</span> |
| <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> |
| <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> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| Had our function been written as taking a <code class="computeroutput"><span class="keyword">float</span></code> |
| rather than a <code class="computeroutput"><span class="keyword">double</span></code>, we could |
| have written instead: |
| </p> |
| <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> |
| |
| <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> |
| <span class="special">{</span> |
| <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> |
| <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> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| Likewise, constants that are suitable for use at <code class="computeroutput"><span class="keyword">long</span> |
| <span class="keyword">double</span></code> precision are available in |
| 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>. |
| </p> |
| <p> |
| You can see the full list of available constants at <a class="link" href="../constants.html" title="The Mathematical Constants">math_toolkit.constants</a>. |
| </p> |
| <p> |
| Some examples of using constants are at <a href="../../../../example/constants_eg1.cpp" target="_top">constants_eg1</a>. |
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