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| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="spirit.advanced.customize.iterate.deref_iterator"></a><a class="link" href="deref_iterator.html" title="Dereference the Iterator pointing into a Container Attribute">Dereference |
| the Iterator pointing into a Container Attribute</a> |
| </h5></div></div></div> |
| <a name="spirit.advanced.customize.iterate.deref_iterator.deref_iterator"></a><h6> |
| <a name="id1192619"></a> |
| <a class="link" href="deref_iterator.html#spirit.advanced.customize.iterate.deref_iterator.deref_iterator">deref_iterator</a> |
| </h6> |
| <p> |
| The template <code class="computeroutput"><span class="identifier">deref_iterator</span></code> |
| is a type used as an attribute customization point. It is invoked by |
| the <span class="emphasis"><em>Karma</em></span> repetitive generators (such as <a class="link" href="../../../karma/reference/operator/list.html" title="Lists (a % b)">List |
| (<code class="computeroutput"><span class="special">%</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/kleene.html" title="Kleene Star (*a)">Kleene |
| (unary <code class="computeroutput"><span class="special">*</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/plus.html" title="Plus (+a)">Plus (unary <code class="computeroutput"><span class="special">+</span></code>)</a>, and <a class="link" href="../../../karma/reference/directive/repeat.html" title="Repetition Directive (repeat[])">Repeat</a>) |
| in order to dereference an iterator pointing to an element of a container |
| holding the attributes to generate output from. |
| </p> |
| <a name="spirit.advanced.customize.iterate.deref_iterator.module_headers"></a><h6> |
| <a name="id1192692"></a> |
| <a class="link" href="deref_iterator.html#spirit.advanced.customize.iterate.deref_iterator.module_headers">Module |
| Headers</a> |
| </h6> |
| <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">spirit</span><span class="special">/</span><span class="identifier">home</span><span class="special">/</span><span class="identifier">support</span><span class="special">/</span><span class="identifier">container</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| </pre> |
| <p> |
| Also, see <a class="link" href="../../../structure/include.html" title="Include">Include Structure</a>. |
| </p> |
| <div class="note"><table border="0" summary="Note"> |
| <tr> |
| <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../images/note.png"></td> |
| <th align="left">Note</th> |
| </tr> |
| <tr><td align="left" valign="top"><p> |
| This header file does not need to be included directly by any user |
| program as it is normally included by other Spirit header files relying |
| on its content. |
| </p></td></tr> |
| </table></div> |
| <a name="spirit.advanced.customize.iterate.deref_iterator.namespace"></a><h6> |
| <a name="id1193882"></a> |
| <a class="link" href="deref_iterator.html#spirit.advanced.customize.iterate.deref_iterator.namespace">Namespace</a> |
| </h6> |
| <div class="informaltable"><table class="table"> |
| <colgroup><col></colgroup> |
| <thead><tr><th> |
| <p> |
| Name |
| </p> |
| </th></tr></thead> |
| <tbody><tr><td> |
| <p> |
| <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">traits</span></code> |
| </p> |
| </td></tr></tbody> |
| </table></div> |
| <a name="spirit.advanced.customize.iterate.deref_iterator.synopsis"></a><h6> |
| <a name="id1193960"></a> |
| <a class="link" href="deref_iterator.html#spirit.advanced.customize.iterate.deref_iterator.synopsis">Synopsis</a> |
| </h6> |
| <pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Iterator</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Enable</span><span class="special">></span> |
| <span class="keyword">struct</span> <span class="identifier">deref_iterator</span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="special"><</span><span class="identifier">unspecified</span><span class="special">></span> <span class="identifier">type</span><span class="special">;</span> |
| <span class="keyword">static</span> <span class="identifier">type</span> <span class="identifier">call</span><span class="special">(</span><span class="identifier">Iterator</span><span class="special">&</span> <span class="identifier">it</span><span class="special">);</span> |
| <span class="special">};</span> |
| </pre> |
| <a name="spirit.advanced.customize.iterate.deref_iterator.template_parameters"></a><h6> |
| <a name="id1194092"></a> |
| <a class="link" href="deref_iterator.html#spirit.advanced.customize.iterate.deref_iterator.template_parameters">Template |
| parameters</a> |
| </h6> |
| <div class="informaltable"><table class="table"> |
| <colgroup> |
| <col> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| <p> |
| Parameter |
| </p> |
| </th> |
| <th> |
| <p> |
| Description |
| </p> |
| </th> |
| <th> |
| <p> |
| Default |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="identifier">Iterator</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| The type, <code class="computeroutput"><span class="identifier">Iterator</span></code> |
| of the iterator to dereference. This is the same as the type |
| returned by the customization point <a class="link" href="container_iterator.html" title="Determine the Type of the Iterator of a Container (Karma)"><code class="computeroutput"><span class="identifier">container_iterator</span></code></a>. |
| </p> |
| </td> |
| <td> |
| <p> |
| none |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="identifier">Enable</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Helper template parameter usable to selectively enable or disable |
| certain specializations of <code class="computeroutput"><span class="identifier">deref_iterator</span></code> |
| utilizing SFINAE (i.e. <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">enable_if</span></code> |
| or <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">disable_if</span></code>). |
| </p> |
| </td> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="keyword">void</span></code> |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| <a name="spirit.advanced.customize.iterate.deref_iterator.notation"></a><h6> |
| <a name="id1194274"></a> |
| <a class="link" href="deref_iterator.html#spirit.advanced.customize.iterate.deref_iterator.notation">Notation</a> |
| </h6> |
| <div class="variablelist"> |
| <p class="title"><b></b></p> |
| <dl> |
| <dt><span class="term"><code class="computeroutput"><span class="identifier">Iterator</span></code></span></dt> |
| <dd><p> |
| An iterator type. |
| </p></dd> |
| <dt><span class="term"><code class="computeroutput"><span class="identifier">it</span></code></span></dt> |
| <dd><p> |
| An instance of an iterator of type <code class="computeroutput"><span class="identifier">Iterator</span></code>. |
| </p></dd> |
| <dt><span class="term"><code class="computeroutput"><span class="identifier">C</span></code></span></dt> |
| <dd><p> |
| A container type whose iterator type is <code class="computeroutput"><span class="identifier">Iterator</span></code>. |
| </p></dd> |
| </dl> |
| </div> |
| <a name="spirit.advanced.customize.iterate.deref_iterator.expression_semantics"></a><h6> |
| <a name="id1194369"></a> |
| <a class="link" href="deref_iterator.html#spirit.advanced.customize.iterate.deref_iterator.expression_semantics">Expression |
| Semantics</a> |
| </h6> |
| <div class="informaltable"><table class="table"> |
| <colgroup> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| <p> |
| Expression |
| </p> |
| </th> |
| <th> |
| <p> |
| Semantics |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="identifier">deref_iterator</span><span class="special"><</span><span class="identifier">Iterator</span><span class="special">>::</span><span class="identifier">type</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Metafunction result evaluating to the type returned by dereferencing |
| the iterator. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="identifier">deref_iterator</span><span class="special"><</span><span class="identifier">Iterator</span><span class="special">>::</span><span class="identifier">call</span><span class="special">(</span><span class="identifier">it</span><span class="special">)</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Return the element in the container referred to by the iterator. |
| The type of the returned value is the same as returned by the |
| metafunction result <code class="computeroutput"><span class="identifier">type</span></code>. |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| <a name="spirit.advanced.customize.iterate.deref_iterator.predefined_specializations"></a><h6> |
| <a name="id1194514"></a> |
| <a class="link" href="deref_iterator.html#spirit.advanced.customize.iterate.deref_iterator.predefined_specializations">Predefined |
| Specializations</a> |
| </h6> |
| <p> |
| <a href="http://boost-spirit.com" target="_top">Spirit</a> predefines specializations |
| of this customization point for several types. The following table lists |
| those types together with the types returned by the embedded typedef |
| <code class="computeroutput"><span class="identifier">type</span></code>: |
| </p> |
| <div class="informaltable"><table class="table"> |
| <colgroup> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| <p> |
| Template Parameters |
| </p> |
| </th> |
| <th> |
| <p> |
| Value |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="identifier">Iterator</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| The metafunction result <code class="computeroutput"><span class="identifier">type</span></code> |
| evaluates to <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">detail</span><span class="special">::</span><span class="identifier">iterator_traits</span><span class="special"><</span><span class="identifier">Iterator</span><span class="special">>::</span><span class="identifier">reference</span></code> |
| and the function <code class="computeroutput"><span class="identifier">call</span><span class="special">()</span></code> returns <code class="computeroutput"><span class="special">*</span><span class="identifier">it</span></code>. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="identifier">unused_type</span></code><code class="computeroutput"> |
| <span class="keyword">const</span><span class="special">*</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| The metafunction result <code class="computeroutput"><span class="identifier">type</span></code> |
| evaluates to <code class="computeroutput"><span class="identifier">unused_type</span></code> |
| and the function <code class="computeroutput"><span class="identifier">call</span><span class="special">()</span></code> returns <code class="computeroutput"><span class="identifier">unused</span></code>. |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| <a name="spirit.advanced.customize.iterate.deref_iterator.when_to_implement"></a><h6> |
| <a name="id1194738"></a> |
| <a class="link" href="deref_iterator.html#spirit.advanced.customize.iterate.deref_iterator.when_to_implement">When |
| to implement</a> |
| </h6> |
| <p> |
| The customization point <code class="computeroutput"><span class="identifier">deref_iterator</span></code> |
| needs to be implemented for a specific iterator type whenever the container |
| this iterator belongs to is to be used as an attribute in place of a |
| STL container. It is applicable for generators (<span class="emphasis"><em>Spirit.Karma</em></span>) |
| only. As a rule of thumb: it has to be implemented whenever a certain |
| iterator type belongs to a container which is to be passed as an attribute |
| to a generator normally exposing a STL container, <code class="computeroutput"><span class="identifier">C</span></code> |
| and if the container type does not expose the interface of a STL container |
| (i.e. <code class="computeroutput"><span class="identifier">is_container</span><span class="special"><</span><span class="identifier">C</span><span class="special">>::</span><span class="identifier">type</span></code> would normally return <code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">false_</span></code>). |
| </p> |
| <a name="spirit.advanced.customize.iterate.deref_iterator.related_attribute_customization_points"></a><h6> |
| <a name="id1194808"></a> |
| <a class="link" href="deref_iterator.html#spirit.advanced.customize.iterate.deref_iterator.related_attribute_customization_points">Related |
| Attribute Customization Points</a> |
| </h6> |
| <p> |
| If this customization point is implemented, the following other customization |
| points might need to be implemented as well. |
| </p> |
| <div class="informaltable"><table class="table"> |
| <colgroup> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| <p> |
| Name |
| </p> |
| </th> |
| <th> |
| <p> |
| When to implement |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| <a class="link" href="../is_container.html" title="Determine if a Type Should be Treated as a Container (Qi and Karma)"><code class="computeroutput"><span class="identifier">is_container</span></code></a> |
| </p> |
| </td> |
| <td> |
| <p> |
| Needs to be implemented whenever a type is to be used as a |
| container attribute in <span class="emphasis"><em>Karma</em></span>. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <a class="link" href="container_iterator.html" title="Determine the Type of the Iterator of a Container (Karma)"><code class="computeroutput"><span class="identifier">container_iterator</span></code></a> |
| </p> |
| </td> |
| <td> |
| <p> |
| Karma: <a class="link" href="../../../karma/reference/operator/list.html" title="Lists (a % b)">List |
| (<code class="computeroutput"><span class="special">%</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/kleene.html" title="Kleene Star (*a)">Kleene (unary |
| <code class="computeroutput"><span class="special">*</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/plus.html" title="Plus (+a)">Plus (unary |
| <code class="computeroutput"><span class="special">+</span></code>)</a>, <a class="link" href="../../../karma/reference/directive/repeat.html" title="Repetition Directive (repeat[])">Repeat</a>. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <a class="link" href="begin_container.html" title="Get the Iterator pointing to the Begin of a Container Attribute"><code class="computeroutput"><span class="identifier">begin_container</span></code></a> |
| </p> |
| </td> |
| <td> |
| <p> |
| Karma: <a class="link" href="../../../karma/reference/operator/list.html" title="Lists (a % b)">List |
| (<code class="computeroutput"><span class="special">%</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/kleene.html" title="Kleene Star (*a)">Kleene (unary |
| <code class="computeroutput"><span class="special">*</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/plus.html" title="Plus (+a)">Plus (unary |
| <code class="computeroutput"><span class="special">+</span></code>)</a>, <a class="link" href="../../../karma/reference/directive/repeat.html" title="Repetition Directive (repeat[])">Repeat</a>. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <a class="link" href="end_container.html" title="Get the Iterator pointing to the End of a Container Attribute"><code class="computeroutput"><span class="identifier">end_container</span></code></a> |
| </p> |
| </td> |
| <td> |
| <p> |
| Karma: <a class="link" href="../../../karma/reference/operator/list.html" title="Lists (a % b)">List |
| (<code class="computeroutput"><span class="special">%</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/kleene.html" title="Kleene Star (*a)">Kleene (unary |
| <code class="computeroutput"><span class="special">*</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/plus.html" title="Plus (+a)">Plus (unary |
| <code class="computeroutput"><span class="special">+</span></code>)</a>, <a class="link" href="../../../karma/reference/directive/repeat.html" title="Repetition Directive (repeat[])">Repeat</a>. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <a class="link" href="deref_iterator.html" title="Dereference the Iterator pointing into a Container Attribute"><code class="computeroutput"><span class="identifier">deref_iterator</span></code></a> |
| </p> |
| </td> |
| <td> |
| <p> |
| Karma: <a class="link" href="../../../karma/reference/operator/list.html" title="Lists (a % b)">List |
| (<code class="computeroutput"><span class="special">%</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/kleene.html" title="Kleene Star (*a)">Kleene (unary |
| <code class="computeroutput"><span class="special">*</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/plus.html" title="Plus (+a)">Plus (unary |
| <code class="computeroutput"><span class="special">+</span></code>)</a>, <a class="link" href="../../../karma/reference/directive/repeat.html" title="Repetition Directive (repeat[])">Repeat</a>. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <a class="link" href="next_iterator.html" title="Increment the Iterator pointing into a Container Attribute"><code class="computeroutput"><span class="identifier">next_iterator</span></code></a> |
| </p> |
| </td> |
| <td> |
| <p> |
| Karma: <a class="link" href="../../../karma/reference/operator/list.html" title="Lists (a % b)">List |
| (<code class="computeroutput"><span class="special">%</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/kleene.html" title="Kleene Star (*a)">Kleene (unary |
| <code class="computeroutput"><span class="special">*</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/plus.html" title="Plus (+a)">Plus (unary |
| <code class="computeroutput"><span class="special">+</span></code>)</a>, <a class="link" href="../../../karma/reference/directive/repeat.html" title="Repetition Directive (repeat[])">Repeat</a>. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <a class="link" href="compare_iterators.html" title="Compare two Iterator pointing into a Container Attribute for Equality"><code class="computeroutput"><span class="identifier">compare_iterators</span></code></a> |
| </p> |
| </td> |
| <td> |
| <p> |
| Karma: <a class="link" href="../../../karma/reference/operator/list.html" title="Lists (a % b)">List |
| (<code class="computeroutput"><span class="special">%</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/kleene.html" title="Kleene Star (*a)">Kleene (unary |
| <code class="computeroutput"><span class="special">*</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/plus.html" title="Plus (+a)">Plus (unary |
| <code class="computeroutput"><span class="special">+</span></code>)</a>, <a class="link" href="../../../karma/reference/directive/repeat.html" title="Repetition Directive (repeat[])">Repeat</a>. |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| <a name="spirit.advanced.customize.iterate.deref_iterator.example"></a><h6> |
| <a name="id1195305"></a> |
| <a class="link" href="deref_iterator.html#spirit.advanced.customize.iterate.deref_iterator.example">Example</a> |
| </h6> |
| <p> |
| Here are the header files needed to make the example code below compile: |
| </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">spirit</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">karma</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">vector</span><span class="special">></span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| The example (for the full source code please see here: <a href="../../../../../../example/karma/customize_counter.cpp" target="_top">customize_counter.cpp</a>) |
| uses the data structure |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">client</span> |
| <span class="special">{</span> |
| <span class="keyword">struct</span> <span class="identifier">counter</span> |
| <span class="special">{</span> |
| <span class="comment">// expose the current value of the counter as our iterator |
| </span> <span class="keyword">typedef</span> <span class="keyword">int</span> <span class="identifier">iterator</span><span class="special">;</span> |
| |
| <span class="comment">// expose 'int' as the type of each generated element |
| </span> <span class="keyword">typedef</span> <span class="keyword">int</span> <span class="identifier">type</span><span class="special">;</span> |
| |
| <span class="identifier">counter</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">max_count</span><span class="special">)</span> |
| <span class="special">:</span> <span class="identifier">counter_</span><span class="special">(</span><span class="number">0</span><span class="special">),</span> <span class="identifier">max_count_</span><span class="special">(</span><span class="identifier">max_count</span><span class="special">)</span> |
| <span class="special">{}</span> |
| |
| <span class="keyword">int</span> <span class="identifier">counter_</span><span class="special">;</span> |
| <span class="keyword">int</span> <span class="identifier">max_count_</span><span class="special">;</span> |
| <span class="special">};</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| as a direct attribute to the <a class="link" href="../../../karma/reference/operator/list.html" title="Lists (a % b)">List |
| (<code class="computeroutput"><span class="special">%</span></code>)</a> generator. This |
| type does not expose any of the interfaces of an STL container. It does |
| not even expose the usual semantics of a container. The presented customization |
| points build a counter instance which is incremented each time it is |
| accessed. The examples shows how to enable its use as an attribute to |
| <span class="emphasis"><em>Karma's</em></span> repetitive generators. |
| </p> |
| <p> |
| In order to make this data structure compatible we need to specialize |
| a couple of attribute customization points: <a class="link" href="../is_container.html" title="Determine if a Type Should be Treated as a Container (Qi and Karma)"><code class="computeroutput"><span class="identifier">is_container</span></code></a>, <a class="link" href="container_iterator.html" title="Determine the Type of the Iterator of a Container (Karma)"><code class="computeroutput"><span class="identifier">container_iterator</span></code></a>, <a class="link" href="begin_container.html" title="Get the Iterator pointing to the Begin of a Container Attribute"><code class="computeroutput"><span class="identifier">begin_container</span></code></a>, and <a class="link" href="end_container.html" title="Get the Iterator pointing to the End of a Container Attribute"><code class="computeroutput"><span class="identifier">end_container</span></code></a>. In addition, |
| we specialize one of the iterator related customization points as well: |
| <a class="link" href="deref_iterator.html" title="Dereference the Iterator pointing into a Container Attribute"><code class="computeroutput"><span class="identifier">deref_iterator</span></code></a>. |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="comment">// All specializations of attribute customization points have to be placed into |
| </span><span class="comment">// the namespace boost::spirit::traits. |
| </span><span class="comment">// |
| </span><span class="comment">// Note that all templates below are specialized using the 'const' type. |
| </span><span class="comment">// This is necessary as all attributes in Karma are 'const'. |
| </span><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">spirit</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">traits</span> |
| <span class="special">{</span> |
| <span class="comment">// The specialization of the template 'is_container<>' will tell the |
| </span> <span class="comment">// library to treat the type 'client::counter' as a container providing |
| </span> <span class="comment">// the items to generate output from. |
| </span> <span class="keyword">template</span> <span class="special"><></span> |
| <span class="keyword">struct</span> <span class="identifier">is_container</span><span class="special"><</span><span class="identifier">client</span><span class="special">::</span><span class="identifier">counter</span> <span class="keyword">const</span><span class="special">></span> |
| <span class="special">:</span> <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">true_</span> |
| <span class="special">{};</span> |
| |
| <span class="comment">// The specialization of the template 'container_iterator<>' will be |
| </span> <span class="comment">// invoked by the library to evaluate the iterator type to be used |
| </span> <span class="comment">// for iterating the data elements in the container. |
| </span> <span class="keyword">template</span> <span class="special"><></span> |
| <span class="keyword">struct</span> <span class="identifier">container_iterator</span><span class="special"><</span><span class="identifier">client</span><span class="special">::</span><span class="identifier">counter</span> <span class="keyword">const</span><span class="special">></span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="identifier">client</span><span class="special">::</span><span class="identifier">counter</span><span class="special">::</span><span class="identifier">iterator</span> <span class="identifier">type</span><span class="special">;</span> |
| <span class="special">};</span> |
| |
| <span class="comment">// The specialization of the templates 'begin_container<>' and |
| </span> <span class="comment">// 'end_container<>' below will be used by the library to get the iterators |
| </span> <span class="comment">// pointing to the begin and the end of the data to generate output from. |
| </span> <span class="comment">// These specializations respectively return the initial and maximum |
| </span> <span class="comment">// counter values. |
| </span> <span class="comment">// |
| </span> <span class="comment">// The passed argument refers to the attribute instance passed to the list |
| </span> <span class="comment">// generator. |
| </span> <span class="keyword">template</span> <span class="special"><></span> |
| <span class="keyword">struct</span> <span class="identifier">begin_container</span><span class="special"><</span><span class="identifier">client</span><span class="special">::</span><span class="identifier">counter</span> <span class="keyword">const</span><span class="special">></span> |
| <span class="special">{</span> |
| <span class="keyword">static</span> <span class="identifier">client</span><span class="special">::</span><span class="identifier">counter</span><span class="special">::</span><span class="identifier">iterator</span> |
| <span class="identifier">call</span><span class="special">(</span><span class="identifier">client</span><span class="special">::</span><span class="identifier">counter</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">c</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span> <span class="identifier">c</span><span class="special">.</span><span class="identifier">counter_</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="special">};</span> |
| |
| <span class="keyword">template</span> <span class="special"><></span> |
| <span class="keyword">struct</span> <span class="identifier">end_container</span><span class="special"><</span><span class="identifier">client</span><span class="special">::</span><span class="identifier">counter</span> <span class="keyword">const</span><span class="special">></span> |
| <span class="special">{</span> |
| <span class="keyword">static</span> <span class="identifier">client</span><span class="special">::</span><span class="identifier">counter</span><span class="special">::</span><span class="identifier">iterator</span> |
| <span class="identifier">call</span><span class="special">(</span><span class="identifier">client</span><span class="special">::</span><span class="identifier">counter</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">c</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span> <span class="identifier">c</span><span class="special">.</span><span class="identifier">max_count_</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="special">};</span> |
| <span class="special">}}}</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="comment">// All specializations of attribute customization points have to be placed into |
| </span><span class="comment">// the namespace boost::spirit::traits. |
| </span><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">spirit</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">traits</span> |
| <span class="special">{</span> |
| <span class="comment">// The specialization of the template 'deref_iterator<>' will be used to |
| </span> <span class="comment">// dereference the iterator associated with our counter data structure. |
| </span> <span class="comment">// Since we expose the current value as the iterator we just return the |
| </span> <span class="comment">// current iterator as the return value. |
| </span> <span class="keyword">template</span> <span class="special"><></span> |
| <span class="keyword">struct</span> <span class="identifier">deref_iterator</span><span class="special"><</span><span class="identifier">client</span><span class="special">::</span><span class="identifier">counter</span><span class="special">::</span><span class="identifier">iterator</span><span class="special">></span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="identifier">client</span><span class="special">::</span><span class="identifier">counter</span><span class="special">::</span><span class="identifier">type</span> <span class="identifier">type</span><span class="special">;</span> |
| |
| <span class="keyword">static</span> <span class="identifier">type</span> <span class="identifier">call</span><span class="special">(</span><span class="identifier">client</span><span class="special">::</span><span class="identifier">counter</span><span class="special">::</span><span class="identifier">iterator</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">it</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span> <span class="identifier">it</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="special">};</span> |
| <span class="special">}}}</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| The last code snippet shows an example using an instance of the data |
| structure <code class="computeroutput"><span class="identifier">client</span><span class="special">::</span><span class="identifier">counter</span></code> to generate output from a |
| <a class="link" href="../../../karma/reference/operator/list.html" title="Lists (a % b)">List (<code class="computeroutput"><span class="special">%</span></code>)</a> generator: |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="comment">// use the instance of a 'client::counter' instead of a STL vector |
| </span><span class="identifier">client</span><span class="special">::</span><span class="identifier">counter</span> <span class="identifier">count</span><span class="special">(</span><span class="number">4</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">karma</span><span class="special">::</span><span class="identifier">format</span><span class="special">(</span><span class="identifier">karma</span><span class="special">::</span><span class="identifier">int_</span> <span class="special">%</span> <span class="string">", "</span><span class="special">,</span> <span class="identifier">count</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="comment">// prints: '0, 1, 2, 3' |
| </span></pre> |
| <p> |
| </p> |
| <p> |
| As you can see, the specializations for the customization points as defined |
| above enable the seamless integration of the custom data structure without |
| having to modify the output format or the generator itself. |
| </p> |
| <p> |
| For other examples of how to use the customization point <code class="computeroutput"><span class="identifier">deref_iterator</span></code> please see here: <a class="link" href="next_iterator.html#spirit.advanced.customize.iterate.next_iterator.example">use_as_container</a>. |
| </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> |
| <hr> |
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