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<div class="section">
<div class="titlepage"><div><div><h5 class="title">
<a name="spirit.karma.reference.generator_concepts.generator"></a><a class="link" href="generator.html" title="Generator">Generator</a>
</h5></div></div></div>
<a name="spirit.karma.reference.generator_concepts.generator.description"></a><h6>
<a name="id1027476"></a>
<a class="link" href="generator.html#spirit.karma.reference.generator_concepts.generator.description">Description</a>
</h6>
<p>
The <span class="emphasis"><em>Generator</em></span> is the most fundamental concept. A
Generator has a member function, <code class="computeroutput"><span class="identifier">generate</span></code>,
that accepts an <code class="computeroutput"><span class="identifier">OutputIterator</span></code>
and returns bool as its result. The iterator receives the data being
generated. The Generator's <code class="computeroutput"><span class="identifier">generate</span></code>
member function returns <code class="computeroutput"><span class="keyword">true</span></code>
if the generator succeeds. Each Generator can represent a specific pattern
or algorithm, or it can be a more complex generator formed as a composition
of other Generators.
</p>
<div class="variablelist">
<p class="title"><b>Notation</b></p>
<dl>
<dt><span class="term"><code class="computeroutput"><span class="identifier">g</span></code></span></dt>
<dd><p>
A <code class="computeroutput"><span class="identifier">Generator</span></code>.
</p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">G</span></code></span></dt>
<dd><p>
A <code class="computeroutput"><span class="identifier">Generator</span></code> type.
</p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">OutIter</span></code></span></dt>
<dd><p>
An <code class="computeroutput"><span class="identifier">OutputIterator</span></code>
type.
</p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">sink</span></code></span></dt>
<dd><p>
An <code class="computeroutput"><span class="identifier">OutputIterator</span></code>
instance.
</p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">Context</span></code></span></dt>
<dd><p>
The generator's Context type.
</p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">context</span></code></span></dt>
<dd><p>
The generator's Context, or <code class="computeroutput"><span class="identifier">unused</span></code>.
</p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">delimit</span></code></span></dt>
<dd><p>
A delimiter Generator, or <code class="computeroutput"><span class="identifier">unused</span></code>.
</p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">attrib</span></code></span></dt>
<dd><p>
A Compatible Attributes, or <code class="computeroutput"><span class="identifier">unused</span></code>.
</p></dd>
</dl>
</div>
<a name="spirit.karma.reference.generator_concepts.generator.valid_expressions"></a><h6>
<a name="id1027738"></a>
<a class="link" href="generator.html#spirit.karma.reference.generator_concepts.generator.valid_expressions">Valid
Expressions</a>
</h6>
<p>
In the expressions below, the behavior of the generator, <code class="computeroutput"><span class="identifier">g</span></code>, as well as how <code class="computeroutput"><span class="identifier">delimit</span></code>
and <code class="computeroutput"><span class="identifier">attrib</span></code> are handled
by <code class="computeroutput"><span class="identifier">g</span></code>, are left unspecified
in the base <code class="computeroutput"><span class="identifier">Generator</span></code>
concept. These are specified in subsequent, more refined concepts and
by the actual models therof.
</p>
<p>
For any Generator the following expressions must be valid:
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Expression
</p>
</th>
<th>
<p>
Semantics
</p>
</th>
<th>
<p>
Return type
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="identifier">g</span><span class="special">.</span><span class="identifier">generate</span><span class="special">(</span><span class="identifier">sink</span><span class="special">,</span> <span class="identifier">context</span><span class="special">,</span> <span class="identifier">delimit</span><span class="special">,</span> <span class="identifier">attrib</span><span class="special">)</span></pre>
<p>
</p>
</td>
<td>
<p>
Generate the output sequence by inserting the generated characters/tokens
into <code class="computeroutput"><span class="identifier">sink</span></code>.
Use the <code class="computeroutput"><span class="identifier">delimit</span></code>
generator for delimiting. Return <code class="computeroutput"><span class="keyword">true</span></code>
if successful, otherwise return <code class="computeroutput"><span class="keyword">false</span></code>.
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="keyword">bool</span></code>
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">g</span><span class="special">.</span><span class="identifier">what</span><span class="special">(</span><span class="identifier">context</span><span class="special">)</span></code>
</p>
</td>
<td>
<p>
Get information about a Generator.
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="identifier">info</span></code>
</p>
</td>
</tr>
</tbody>
</table></div>
<a name="spirit.karma.reference.generator_concepts.generator.type_expressions"></a><h6>
<a name="id1028007"></a>
<a class="link" href="generator.html#spirit.karma.reference.generator_concepts.generator.type_expressions">Type
Expressions</a>
</h6>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Expression
</p>
</th>
<th>
<p>
Description
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">G</span><span class="special">::</span><span class="keyword">template</span> <span class="identifier">attribute</span><span class="special"><</span><span class="identifier">Context</span><span class="special">>::</span><span class="identifier">type</span></code>
</p>
</td>
<td>
<p>
The Generator's attribute.
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">is_generator</span><span class="special"><</span><span class="identifier">G</span><span class="special">>::</span><span class="identifier">type</span></code>
</p>
</td>
<td>
<p>
Metafunction that evaluates to <code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">true_</span></code>
if a certain type, <code class="computeroutput"><span class="identifier">G</span></code>
is a Generator, <code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">false_</span></code>
otherwise (See <a href="../../../../../../../../libs/mpl/doc/refmanual/integral-constant.html" target="_top">MPL
Boolean Constant</a>).
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">G</span><span class="special">::</span><span class="identifier">properties</span></code>
</p>
</td>
<td>
<p>
An <code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">int_</span></code> (See <a href="../../../../../../../../libs/mpl/doc/refmanual/integral-constant.html" target="_top">MPL
Integral Constant</a>) holding a value from the <code class="computeroutput"><span class="identifier">karma</span><span class="special">::</span><span class="identifier">generator_properties</span></code> enumeration.
The default value is <code class="computeroutput"><span class="identifier">generator_properties</span><span class="special">::</span><span class="identifier">no_properties</span></code>
</p>
</td>
</tr>
</tbody>
</table></div>
<a name="spirit.karma.reference.generator_concepts.generator.postcondition"></a><h6>
<a name="id1028278"></a>
<a class="link" href="generator.html#spirit.karma.reference.generator_concepts.generator.postcondition">Postcondition</a>
</h6>
<p>
Upon return from <code class="computeroutput"><span class="identifier">g</span><span class="special">.</span><span class="identifier">generate</span></code> the following post conditions
should hold:
</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
On successful generation, <code class="computeroutput"><span class="identifier">sink</span></code>
receives the generated characters/tokens sequence.
</li>
<li class="listitem">
No pre-delimits: <code class="computeroutput"><span class="identifier">delimit</span></code>
characters/tokens will not be emitted in front of any other output.
</li>
<li class="listitem">
The attribute <code class="computeroutput"><span class="identifier">attrib</span></code>
has not been modified.
</li>
</ul></div>
<a name="spirit.karma.reference.generator_concepts.generator.models"></a><h6>
<a name="id1028359"></a>
<a class="link" href="generator.html#spirit.karma.reference.generator_concepts.generator.models">Models</a>
</h6>
<p>
All generators in <span class="emphasis"><em>Spirit.Karma</em></span> are models of the
<span class="emphasis"><em>Generator</em></span> concept.
</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 © 2001-2010 Joel de Guzman, Hartmut Kaiser<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>
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