<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> <title>Setting Polices at Namespace Scope</title> <link rel="stylesheet" href="../../../../../../../../doc/src/boostbook.css" type="text/css"> <meta name="generator" content="DocBook XSL Stylesheets V1.74.0"> <link rel="home" href="../../../index.html" title="Math Toolkit"> <link rel="up" href="../pol_ref.html" title="Policy Reference"> <link rel="prev" href="policy_defaults.html" title="Using macros to Change the Policy Defaults"> <link rel="next" href="pol_ref_ref.html" title="Policy Class Reference"> </head> <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> <table cellpadding="2" width="100%"><tr> <td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../../boost.png"></td> <td align="center"><a href="../../../../../../../../index.html">Home</a></td> <td align="center"><a href="../../../../../../../../libs/libraries.htm">Libraries</a></td> <td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> <td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> <td align="center"><a href="../../../../../../../../more/index.htm">More</a></td> </tr></table> <hr> <div class="spirit-nav"> <a accesskey="p" href="policy_defaults.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../pol_ref.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="pol_ref_ref.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> </div> <div class="section" lang="en"> <div class="titlepage"><div><div><h4 class="title"> <a name="math_toolkit.policy.pol_ref.namespace_pol"></a><a class="link" href="namespace_pol.html" title="Setting Polices at Namespace Scope"> Setting Polices at Namespace Scope</a> </h4></div></div></div> <p> Sometimes what you really want to do is bring all the special functions, or all the distributions into a specific namespace-scope, along with a specific policy to use with them. There are two macros defined to assist with that: </p> <pre class="programlisting"><span class="identifier">BOOST_MATH_DECLARE_SPECIAL_FUNCTIONS</span><span class="special">(</span><span class="identifier">Policy</span><span class="special">)</span> </pre> <p> and: </p> <pre class="programlisting"><span class="identifier">BOOST_MATH_DECLARE_DISTRIBUTIONS</span><span class="special">(</span><span class="identifier">Type</span><span class="special">,</span> <span class="identifier">Policy</span><span class="special">)</span> </pre> <p> You can use either of these macros after including any special function or distribution header. For example: </p> <p> </p> <p> </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">special_functions</span><span class="special">/</span><span class="identifier">gamma</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> <span class="keyword">namespace</span> <span class="identifier">myspace</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">policies</span><span class="special">;</span> <span class="comment">// Define a policy that does not throw on overflow: </span><span class="keyword">typedef</span> <span class="identifier">policy</span><span class="special"><</span><span class="identifier">overflow_error</span><span class="special"><</span><span class="identifier">errno_on_error</span><span class="special">></span> <span class="special">></span> <span class="identifier">my_policy</span><span class="special">;</span> <span class="comment">// Define the special functions in this scope to use the policy: </span><span class="identifier">BOOST_MATH_DECLARE_SPECIAL_FUNCTIONS</span><span class="special">(</span><span class="identifier">my_policy</span><span class="special">)</span> <span class="special">}</span> <span class="comment">// </span><span class="comment">// Now we can use myspace::tgamma etc. </span><span class="comment">// They will automatically use "my_policy": </span><span class="comment">// </span><span class="keyword">double</span> <span class="identifier">t</span> <span class="special">=</span> <span class="identifier">myspace</span><span class="special">::</span><span class="identifier">tgamma</span><span class="special">(</span><span class="number">30.0</span><span class="special">);</span> <span class="comment">// will not throw on overflow </span> </pre> <p> </p> <p> </p> <p> In this example, using BOOST_MATH_DECLARE_SPECIAL_FUNCTIONS results in a set of thin inline forwarding functions being defined: </p> <pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> <span class="keyword">inline</span> <span class="identifier">T</span> <span class="identifier">tgamma</span><span class="special">(</span><span class="identifier">T</span> <span class="identifier">a</span><span class="special">){</span> <span class="keyword">return</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">tgamma</span><span class="special">(</span><span class="identifier">a</span><span class="special">,</span> <span class="identifier">mypolicy</span><span class="special">());</span> <span class="special">}</span> <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> <span class="keyword">inline</span> <span class="identifier">T</span> <span class="identifier">lgamma</span><span class="special">(</span><span class="identifier">T</span> <span class="identifier">a</span><span class="special">)</span> <span class="special">(</span> <span class="keyword">return</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">lgamma</span><span class="special">(</span><span class="identifier">a</span><span class="special">,</span> <span class="identifier">mypolicy</span><span class="special">());</span> <span class="special">}</span> </pre> <p> and so on. Note that while a forwarding function is defined for all the special functions, however, unless you include the specific header for the special function you use (or boost/math/special_functions.hpp to include everything), you will get linker errors from functions that are forward declared, but not defined. </p> <p> We can do the same thing with the distributions, but this time we need to specify the floating-point type to use: </p> <p> </p> <p> </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">distributions</span><span class="special">/</span><span class="identifier">cauchy</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> <span class="keyword">namespace</span> <span class="identifier">myspace</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">policies</span><span class="special">;</span> <span class="comment">// Define a policy to use, in this case we want all the distribution </span><span class="comment">// accessor functions to compile, even if they are mathematically </span><span class="comment">// undefined: </span><span class="keyword">typedef</span> <span class="identifier">policy</span><span class="special"><</span><span class="identifier">assert_undefined</span><span class="special"><</span><span class="keyword">false</span><span class="special">></span> <span class="special">></span> <span class="identifier">my_policy</span><span class="special">;</span> <span class="identifier">BOOST_MATH_DECLARE_DISTRIBUTIONS</span><span class="special">(</span><span class="keyword">double</span><span class="special">,</span> <span class="identifier">my_policy</span><span class="special">)</span> <span class="special">}</span> <span class="comment">// Now we can use myspace::cauchy etc, which will use policy </span><span class="comment">// myspace::mypolicy: </span><span class="comment">// </span><span class="comment">// This compiles but raises a domain error at runtime: </span><span class="comment">// </span><span class="keyword">void</span> <span class="identifier">test_cauchy</span><span class="special">()</span> <span class="special">{</span> <span class="keyword">try</span> <span class="special">{</span> <span class="keyword">double</span> <span class="identifier">d</span> <span class="special">=</span> <span class="identifier">mean</span><span class="special">(</span><span class="identifier">myspace</span><span class="special">::</span><span class="identifier">cauchy</span><span class="special">());</span> <span class="special">}</span> <span class="keyword">catch</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">domain_error</span><span class="special">&</span> <span class="identifier">e</span><span class="special">)</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">e</span><span class="special">.</span><span class="identifier">what</span><span class="special">()</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="special">}</span> <span class="special">}</span> </pre> <p> </p> <p> </p> <p> In this example the result of BOOST_MATH_DECLARE_DISTRIBUTIONS is to declare a typedef for each distribution like this: </p> <pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">cauchy_distribution</span><span class="special"><</span><span class="keyword">double</span><span class="special">,</span> <span class="identifier">my_policy</span><span class="special">></span> <span class="identifier">cauchy</span><span class="special">;</span> <span class="identifier">tyepdef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">gamma_distribution</span><span class="special"><</span><span class="keyword">double</span><span class="special">,</span> <span class="identifier">my_policy</span><span class="special">></span> <span class="identifier">gamma</span><span class="special">;</span> </pre> <p> and so on. The name given to each typedef is the name of the distribution with the "_distribution" suffix removed. </p> </div> <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> <td align="left"></td> <td align="right"><div class="copyright-footer">Copyright © 2006 , 2007, 2008, 2009 John Maddock, Paul A. Bristow, Hubert Holin, Xiaogang Zhang, Bruno Lalande, Johan Råde, Gautam Sewani and Thijs van den Berg<p> Distributed under the Boost Software License, Version 1.0. (See accompanying 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>) </p> </div></td> </tr></table> <hr> <div class="spirit-nav"> <a accesskey="p" href="policy_defaults.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../pol_ref.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="pol_ref_ref.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> </div> </body> </html>