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<div class="titlepage"><div><div><h3 class="title">
<a name="math_toolkit.using_udt.archetypes"></a><a class="link" href="archetypes.html" title="Conceptual Archetypes and Testing"> Conceptual Archetypes
and Testing</a>
</h3></div></div></div>
<p>
There are several concept archetypes available:
</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">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>
<p>
</p>
<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="comment">// namespaces
</span></pre>
<p>
<code class="computeroutput"><span class="identifier">std_real_concept</span></code> is an archetype
for the built-in Real types.
</p>
<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 using declaration to make them visible
in the current scope. Unfortunately it's all to easy to forget the using
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>
<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 it's usage of
standard library functions.
</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">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>
<p>
</p>
<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="concepts.html" title="Conceptual Requirements for Real Number Types">user defined real types</a>,
it declares it's standard library functions in it's 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 this is not a conceptual requirement for <a class="link" href="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="use_ntl.html" title="Using With NTL - a High-Precision Floating-Point 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>
<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">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>
<p>
</p>
<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>
<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>
<p>
v = pdf(dist, x); // (Result v is ignored).
</p>
<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>
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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>)
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