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- <div class="titlepage"><div><div><h2 class="title" style="clear: both">
- <a name="math_toolkit.archetypes"></a><a class="link" href="archetypes.html" title="Conceptual Archetypes for Reals and Distributions">Conceptual Archetypes for Reals
- and Distributions</a>
- </h2></div></div></div>
- <p>
- There are a few concept archetypes available:
- </p>
- <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
- <li class="listitem">
- Real concept for floating-point types.
- </li>
- <li class="listitem">
- Distribution concept for statistical distributions.
- </li>
- </ul></div>
- <h6>
- <a name="math_toolkit.archetypes.h0"></a>
- <span class="phrase"><a name="math_toolkit.archetypes.real_concept"></a></span><a class="link" href="archetypes.html#math_toolkit.archetypes.real_concept">Real
- concept</a>
- </h6>
- <p>
- <code class="computeroutput"><span class="identifier">std_real_concept</span></code> is an archetype
- for theReal types, including the built-in float, double, long double.
- </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">concepts</span><span class="special">/</span><span class="identifier">std_real_concept</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></pre>
- <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">{</span>
- <span class="keyword">namespace</span> <span class="identifier">math</span><span class="special">{</span>
- <span class="keyword">namespace</span> <span class="identifier">concepts</span>
- <span class="special">{</span>
- <span class="keyword">class</span> <span class="identifier">std_real_concept</span><span class="special">;</span>
- <span class="special">}</span>
- <span class="special">}}</span> <span class="comment">// namespaces</span>
- </pre>
- <p>
- The main purpose in providing this type is to verify that standard library
- functions are found via a using declaration - bringing those functions into
- the current scope - and not just because they happen to be in global scope.
- </p>
- <p>
- In order to ensure that a call to say <code class="computeroutput"><span class="identifier">pow</span></code>
- can be found either via argument dependent lookup, or failing that then in
- the std namespace: all calls to standard library functions are unqualified,
- with the std:: versions found via a <code class="computeroutput"><span class="keyword">using</span></code>
- declaration to make them visible in the current scope. Unfortunately it's all
- to easy to forget the <code class="computeroutput"><span class="keyword">using</span></code> declaration,
- and call the double version of the function that happens to be in the global
- scope by mistake.
- </p>
- <p>
- For example if the code calls ::pow rather than std::pow, the code will cleanly
- compile, but truncation of long doubles to double will cause a significant
- loss of precision. In contrast a template instantiated with std_real_concept
- will <span class="bold"><strong>only</strong></span> compile if the all the standard
- library functions used have been brought into the current scope with a using
- declaration.
- </p>
- <h3>
- <a name="math_toolkit.archetypes.h1"></a>
- <span class="phrase"><a name="math_toolkit.archetypes.testing_the_real_concept"></a></span><a class="link" href="archetypes.html#math_toolkit.archetypes.testing_the_real_concept">Testing
- the real concept</a>
- </h3>
- <p>
- There is a test program <a href="../../../test/std_real_concept_check.cpp" target="_top">libs/math/test/std_real_concept_check.cpp</a>
- that instantiates every template in this library with type <code class="computeroutput"><span class="identifier">std_real_concept</span></code>
- to verify its usage of standard library functions.
- </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">concepts</span><span class="special">/</span><span class="identifier">real_concept</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></pre>
- <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">{</span>
- <span class="keyword">namespace</span> <span class="identifier">math</span><span class="special">{</span>
- <span class="keyword">namespace</span> <span class="identifier">concepts</span><span class="special">{</span>
- <span class="keyword">class</span> <span class="identifier">real_concept</span><span class="special">;</span>
- <span class="special">}}}</span> <span class="comment">// namespaces</span>
- </pre>
- <p>
- <code class="computeroutput"><span class="identifier">real_concept</span></code> is an archetype
- for <a class="link" href="real_concepts.html" title="Conceptual Requirements for Real Number Types">user defined real types</a>,
- it declares its standard library functions in its own namespace: these will
- only be found if they are called unqualified allowing argument dependent lookup
- to locate them. In addition this type is useable at runtime: this allows code
- that would not otherwise be exercised by the built-in floating point types
- to be tested. There is no std::numeric_limits<> support for this type,
- since numeric_limits is not a conceptual requirement for <a class="link" href="real_concepts.html" title="Conceptual Requirements for Real Number Types">RealType</a>s.
- </p>
- <p>
- NTL RR is an example of a type meeting the requirements that this type models,
- but note that use of a thin wrapper class is required: refer to <a class="link" href="high_precision/use_ntl.html" title="Using NTL Library">"Using
- With NTL - a High-Precision Floating-Point Library"</a>.
- </p>
- <p>
- There is no specific test case for type <code class="computeroutput"><span class="identifier">real_concept</span></code>,
- instead, since this type is usable at runtime, each individual test case as
- well as testing <code class="computeroutput"><span class="keyword">float</span></code>, <code class="computeroutput"><span class="keyword">double</span></code> and <code class="computeroutput"><span class="keyword">long</span>
- <span class="keyword">double</span></code>, also tests <code class="computeroutput"><span class="identifier">real_concept</span></code>.
- </p>
- <h3>
- <a name="math_toolkit.archetypes.h2"></a>
- <span class="phrase"><a name="math_toolkit.archetypes.distribution_concept"></a></span><a class="link" href="archetypes.html#math_toolkit.archetypes.distribution_concept">Distribution
- Concept</a>
- </h3>
- <p>
- Distribution Concept models statistical distributions.
- </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">concepts</span><span class="special">/</span><span class="identifier">distribution</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></pre>
- <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">{</span>
- <span class="keyword">namespace</span> <span class="identifier">math</span><span class="special">{</span>
- <span class="keyword">namespace</span> <span class="identifier">concepts</span>
- <span class="special">{</span>
- <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">RealType</span><span class="special">></span>
- <span class="keyword">class</span> <span class="identifier">distribution_archetype</span><span class="special">;</span>
- <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Distribution</span><span class="special">></span>
- <span class="keyword">struct</span> <span class="identifier">DistributionConcept</span><span class="special">;</span>
- <span class="special">}}}</span> <span class="comment">// namespaces</span>
- </pre>
- <p>
- The class template <code class="computeroutput"><span class="identifier">distribution_archetype</span></code>
- is a model of the <a class="link" href="dist_concept.html" title="Conceptual Requirements for Distribution Types">Distribution concept</a>.
- </p>
- <p>
- The class template <code class="computeroutput"><span class="identifier">DistributionConcept</span></code>
- is a <a href="../../../../../libs/concept_check/index.html" target="_top">concept checking
- class</a> for distribution types.
- </p>
- <h3>
- <a name="math_toolkit.archetypes.h3"></a>
- <span class="phrase"><a name="math_toolkit.archetypes.testing_the_distribution_concept"></a></span><a class="link" href="archetypes.html#math_toolkit.archetypes.testing_the_distribution_concept">Testing
- the distribution concept</a>
- </h3>
- <p>
- The test program <a href="../../../test/compile_test/distribution_concept_check.cpp" target="_top">distribution_concept_check.cpp</a>
- is responsible for using <code class="computeroutput"><span class="identifier">DistributionConcept</span></code>
- to verify that all the distributions in this library conform to the <a class="link" href="dist_concept.html" title="Conceptual Requirements for Distribution Types">Distribution
- concept</a>.
- </p>
- <p>
- The class template <code class="computeroutput"><span class="identifier">DistributionConcept</span></code>
- verifies the existence (but not proper function) of the non-member accessors
- required by the <a class="link" href="dist_concept.html" title="Conceptual Requirements for Distribution Types">Distribution concept</a>.
- These are checked by calls like
- </p>
- <pre class="programlisting"><span class="identifier">v</span> <span class="special">=</span> <span class="identifier">pdf</span><span class="special">(</span><span class="identifier">dist</span><span class="special">,</span> <span class="identifier">x</span><span class="special">);</span> <span class="comment">// (Result v is ignored).</span>
- </pre>
- <p>
- And in addition, those that accept two arguments do the right thing when the
- arguments are of different types (the result type is always the same as the
- distribution's value_type). (This is implemented by some additional forwarding-functions
- in derived_accessors.hpp, so that there is no need for any code changes. Likewise
- boilerplate versions of the hazard/chf/coefficient_of_variation functions are
- implemented in there too.)
- </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 © 2006-2019 Nikhar
- Agrawal, Anton Bikineev, Paul A. Bristow, Marco Guazzone, Christopher Kormanyos,
- Hubert Holin, Bruno Lalande, John Maddock, Jeremy Murphy, Matthew Pulver, Johan
- Råde, Gautam Sewani, Benjamin Sobotta, Nicholas Thompson, Thijs van den Berg,
- Daryle Walker and Xiaogang Zhang<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>)
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