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added docs for iterator_traits_generator

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[SVN r9498]
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Jeremy Siek 2001-03-08 19:19:46 +00:00
parent 26240403b0
commit f353415136
1 changed files with 76 additions and 5 deletions
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iterator_adaptors.htm
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@ -129,11 +129,11 @@
<p><tt>iterator_adaptor</tt> is declared like this:
<pre>
template &lt;class Base, class Policies,
class Value = typename std::iterator_traits&lt;Base&gt;::value_type,
class Reference = <i>...(see below)</i>,
class Pointer = <i>...(see below)</i>,
class Category = typename std::iterator_traits&lt;Base&gt;::iterator_category,
class Distance = typename std::iterator_traits&lt;Base&gt;::difference_type&gt;
class ValueOrNamedParams = typename std::iterator_traits&lt;Base&gt;::value_type,
class ReferenceOrNamedParams = <i>...(see below)</i>,
class PointerOrNamedParams = <i>...(see below)</i>,
class CategoryOrNamedParams = typename std::iterator_traits&lt;Base&gt;::iterator_category,
class DistanceOrNamedParams = typename std::iterator_traits&lt;Base&gt;::difference_type&gt;
struct iterator_adaptor;
</pre>
@ -203,8 +203,79 @@ struct iterator_adaptor;
<td>The <tt>difference_type</tt> for the resulting iterator.<br>
<b>Default:</b>
<tt>std::iterator_traits&lt;BaseType&gt;::difference_type</tt>
<tr>
<td><tt>NamedParams</tt>
<td>A list of named template parameters generated using the
<a href="#iterator_traits_generator">
<tt>iterator_traits_generator</tt></a> class (see below).
</table>
<h3><a name="named_template_parameters">Named Template Parameters</a></h3>
With seven template parameters, providing arguments for
<tt>iterator_adaptor</tt> in the correct order can be challenging.
Also, often times one would like to specify the sixth or seventh
template parameter, but use the defaults for the third through
fifth. As a solution to these problems we provide a mechanism for
naming the last five template parameters, and providing them in
any order through the <tt>iterator_traits_generator</tt> class.
<a name="iterator_traits_generator">
<blockquote>
<pre>
class iterator_traits_generator
{
public:
template &lt;class Value&gt;
struct value_type : public <i>recursive magic</i> { };
template &lt;class Reference&gt;
struct reference : public <i>recursive magic</i> { };
template &lt;class Pointer&gt;
struct pointer : public <i>recursive magic</i> { };
template &lt;class Distance&gt;
struct difference_type : public <i>recursive magic</i> { };
template &lt;class Category&gt;
struct iterator_category : public <i>recursive magic</i> { };
};
</pre>
</blockquote>
</a>
The <tt>iterator_traits_generator</tt> is used to create a list of
of template arguments. For example, suppose you want to set the
<tt>Reference</tt> and <tt>Category</tt> parameters, and use the
defaults for the rest. Then you can use the traits generator as
follows:
<blockquote>
<pre>
iterator_traits_generator::reference&lt;foo&gt;::category&lt;std::input_iterator_tag&gt;
</pre>
</blockquote>
This generated type can then be passed into the
<tt>iterator_adaptor</tt> class to replace any of the last five
parameters. If you use the traits generator in the <i>i</i>th
parameter position, then the parameters <i>i</i> through 7 will
use the types specified in the generator.
<blockquote>
<pre>
iterator_adaptor&lt;foo_iterator, foo_policies,
iterator_traits_generator
::reference&lt;foo&gt;
::category&lt;std::input_iterator_tag&gt;
&gt;
</pre>
</blockquote>
<h3><a name="policies">The Policies Class</a></h3>
<p>The main task in using <tt>iterator_adaptor</tt> is creating an