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| All macros of the type <code class="computeroutput"><span class="identifier">BOOST_FLOAT16_C</span><span class="special">,</span> <span class="identifier">BOOST_FLOAT32_C</span><span class="special">,</span> <span class="identifier">BOOST_FLOAT64_C</span><span class="special">,</span> <span class="identifier">BOOST_FLOAT80_C</span><span class="special">,</span> <span class="identifier">BOOST_FLOAT128_C</span><span class="special">,</span> </code> and <code class="computeroutput"><span class="identifier">BOOST_FLOATMAX_C</span></code> |
| are always defined after inclusion of <code class="computeroutput"><span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">cstdfloat</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></code>. |
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| These allow floating-point <span class="bold"><strong>constants of at least the |
| specified width</strong></span> to be declared: |
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| <pre class="programlisting"><span class="comment">// Declare Archimedes' constant using float32_t with approximately 7 decimal digits of precision.</span> |
| <span class="keyword">static</span> <span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">float32_t</span> <span class="identifier">pi</span> <span class="special">=</span> <span class="identifier">BOOST_FLOAT32_C</span><span class="special">(</span><span class="number">3.1415926536</span><span class="special">);</span> |
| |
| <span class="comment">// Declare the Euler-gamma constant with approximately 15 decimal digits of precision.</span> |
| <span class="keyword">static</span> <span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">float64_t</span> <span class="identifier">euler</span> <span class="special">=</span> |
| <span class="identifier">BOOST_FLOAT64_C</span><span class="special">(</span><span class="number">0.57721566490153286060651209008240243104216</span><span class="special">);</span> |
| |
| <span class="comment">// Declare the Golden Ratio constant with the maximum decimal digits of precision that the platform supports.</span> |
| <span class="keyword">static</span> <span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">floatmax_t</span> <span class="identifier">golden_ratio</span> <span class="special">=</span> |
| <span class="identifier">BOOST_FLOATMAX_C</span><span class="special">(</span><span class="number">1.61803398874989484820458683436563811772</span><span class="special">);</span> |
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| Boost.Math provides many constants 'built-in', so always use Boost.Math constants |
| if available, for example: |
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| <pre class="programlisting"><span class="comment">// Display the constant pi to the maximum available precision.</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">floatmax_t</span> <span class="identifier">pi_max</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">pi</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">floatmax_t</span><span class="special">>();</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span><span class="special">.</span><span class="identifier">precision</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">floatmax_t</span><span class="special">>::</span><span class="identifier">digits10</span><span class="special">);</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Most precise pi = "</span> <span class="special"><<</span> <span class="identifier">pi_max</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> |
| <span class="comment">// If floatmax_t is float_128_t, then </span> |
| <span class="comment">// Most precise pi = 3.141592653589793238462643383279503</span> |
| </pre> |
| <p> |
| from <a href="../../../../example/cstdfloat_example.cpp" target="_top">cstdfloat_example.cpp</a>. |
| </p> |
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