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[boost][range] - Updated begin/end to be protected against accidental ADL to improve compatibility with C++0x. Added any_range which adds type erasure support. Added a type_erased adaptor to utilise the any_range. Implemented the any_iterator using a small buffer optimization to avoid heap usage. [SVN r67541]
2011-01-01 16:46:32 +00:00
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<div class="titlepage"><div><div><h4 class="title">
<a name="range.reference.ranges.any_range"></a><a class="link" href="any_range.html" title="any_range">any_range</a>
</h4></div></div></div>
<a name="range.reference.ranges.any_range.description"></a><h6>
<a name="id754843"></a>
<a class="link" href="any_range.html#range.reference.ranges.any_range.description">Description</a>
</h6>
<p>
<code class="computeroutput"><span class="identifier">any_range</span></code> is a range that
has the type information erased hence a <code class="computeroutput"><span class="identifier">any_range</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">forward_pass_traversal_tag</span><span class="special">,</span> <span class="keyword">int</span><span class="special">,</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">ptrdiff_t</span><span class="special">&gt;</span></code>
can be used to represent a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span></code>, a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">list</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span></code> or many other types.
</p>
<p>
The <a href="http://www.artima.com/cppsource/type_erasure.html" target="_top">type
erasure article</a> covers the motivation and goals of type erasure
in this context. Clearly my implementation is building upon a lot of prior
art created by others. Thomas Becker's <code class="computeroutput"><span class="identifier">any_iterator</span></code>
was a strong influence. Adobe also have an <code class="computeroutput"><span class="identifier">any_iterator</span></code>
implementation, but this has very tight coupling to other parts of the
library that precluded it from use in Boost.Range. Early development versions
of this Range Adaptor directly used Thomas Becker's any_iterator implementation.
Subsequently I discovered that the heap allocations of this and many other
implementations cause poor speed performance particularly at the tails
of the distribution. To solve this required a new design that incorporated
the embedded buffer optimization.
</p>
<p>
Despite the underlying <code class="computeroutput"><span class="identifier">any_iterator</span></code>
being the fastest available implementation, the performance overhead of
<code class="computeroutput"><span class="identifier">any_range</span></code> is still appreciable
due to the cost of virtual function calls required to implement <code class="computeroutput"><span class="identifier">increment</span></code>, <code class="computeroutput"><span class="identifier">decrement</span></code>,
<code class="computeroutput"><span class="identifier">advance</span></code>, <code class="computeroutput"><span class="identifier">equal</span></code> etc. Frequently a better design
choice is to convert to a canonical form.
</p>
<p>
Please see the <a class="link" href="../adaptors/reference/type_erased.html" title="type_erased">type_erased</a>
for a Range Adaptor that returns <code class="computeroutput"><span class="identifier">any_range</span></code>
instances.
</p>
<a name="range.reference.ranges.any_range.synopsis"></a><h6>
<a name="id755211"></a>
<a class="link" href="any_range.html#range.reference.ranges.any_range.synopsis">Synopsis</a>
</h6>
<p>
</p>
<pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span>
<span class="keyword">class</span> <span class="identifier">Value</span>
<span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Traversal</span>
<span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Reference</span>
<span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Difference</span>
<span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Buffer</span> <span class="special">=</span> <span class="identifier">any_iterator_default_buffer</span>
<span class="special">&gt;</span>
<span class="keyword">class</span> <span class="identifier">any_range</span>
<span class="special">:</span> <span class="keyword">public</span> <span class="identifier">iterator_range</span><span class="special">&lt;</span>
<span class="identifier">range_detail</span><span class="special">::</span><span class="identifier">any_iterator</span><span class="special">&lt;</span>
<span class="identifier">Value</span>
<span class="special">,</span> <span class="identifier">Traversal</span>
<span class="special">,</span> <span class="identifier">Reference</span>
<span class="special">,</span> <span class="identifier">Difference</span>
<span class="special">,</span> <span class="identifier">Buffer</span>
<span class="special">&gt;</span>
<span class="special">&gt;</span>
<span class="special">{</span>
<span class="keyword">typedef</span> <span class="identifier">range_detail</span><span class="special">::</span><span class="identifier">any_iterator</span><span class="special">&lt;</span>
<span class="identifier">Value</span>
<span class="special">,</span> <span class="identifier">Traversal</span>
<span class="special">,</span> <span class="identifier">Reference</span>
<span class="special">,</span> <span class="identifier">Difference</span>
<span class="special">,</span> <span class="identifier">Buffer</span>
<span class="special">&gt;</span> <span class="identifier">any_iterator_type</span><span class="special">;</span>
<span class="keyword">typedef</span> <span class="identifier">iterator_range</span><span class="special">&lt;</span><span class="identifier">any_iterator_type</span><span class="special">&gt;</span> <span class="identifier">base_type</span><span class="special">;</span>
<span class="keyword">struct</span> <span class="identifier">enabler</span> <span class="special">{};</span>
<span class="keyword">struct</span> <span class="identifier">disabler</span> <span class="special">{};</span>
<span class="keyword">public</span><span class="special">:</span>
<span class="keyword">typedef</span> <span class="identifier">any_iterator_type</span> <span class="identifier">iterator</span><span class="special">;</span>
<span class="keyword">typedef</span> <span class="identifier">any_iterator_type</span> <span class="identifier">const_iterator</span><span class="special">;</span>
<span class="identifier">any_range</span><span class="special">()</span>
<span class="special">{</span>
<span class="special">}</span>
<span class="identifier">any_range</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">any_range</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span>
<span class="special">:</span> <span class="identifier">base_type</span><span class="special">(</span><span class="identifier">other</span><span class="special">)</span>
<span class="special">{</span>
<span class="special">}</span>
<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">WrappedRange</span><span class="special">&gt;</span>
<span class="identifier">any_range</span><span class="special">(</span><span class="identifier">WrappedRange</span><span class="special">&amp;</span> <span class="identifier">wrapped_range</span><span class="special">)</span>
<span class="special">:</span> <span class="identifier">base_type</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">begin</span><span class="special">(</span><span class="identifier">wrapped_range</span><span class="special">),</span>
<span class="identifier">boost</span><span class="special">::</span><span class="identifier">end</span><span class="special">(</span><span class="identifier">wrapped_range</span><span class="special">))</span>
<span class="special">{</span>
<span class="special">}</span>
<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">WrappedRange</span><span class="special">&gt;</span>
<span class="identifier">any_range</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">WrappedRange</span><span class="special">&amp;</span> <span class="identifier">wrapped_range</span><span class="special">)</span>
<span class="special">:</span> <span class="identifier">base_type</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">begin</span><span class="special">(</span><span class="identifier">wrapped_range</span><span class="special">),</span>
<span class="identifier">boost</span><span class="special">::</span><span class="identifier">end</span><span class="special">(</span><span class="identifier">wrapped_range</span><span class="special">))</span>
<span class="special">{</span>
<span class="special">}</span>
<span class="keyword">template</span><span class="special">&lt;</span>
<span class="keyword">class</span> <span class="identifier">OtherValue</span>
<span class="special">,</span> <span class="keyword">class</span> <span class="identifier">OtherTraversal</span>
<span class="special">,</span> <span class="keyword">class</span> <span class="identifier">OtherReference</span>
<span class="special">,</span> <span class="keyword">class</span> <span class="identifier">OtherDifference</span>
<span class="special">&gt;</span>
<span class="identifier">any_range</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">any_range</span><span class="special">&lt;</span>
<span class="identifier">OtherValue</span>
<span class="special">,</span> <span class="identifier">OtherTraversal</span>
<span class="special">,</span> <span class="identifier">OtherReference</span>
<span class="special">,</span> <span class="identifier">OtherDifference</span>
<span class="special">,</span> <span class="identifier">Buffer</span>
<span class="special">&gt;&amp;</span> <span class="identifier">other</span><span class="special">)</span>
<span class="special">:</span> <span class="identifier">base_type</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">begin</span><span class="special">(</span><span class="identifier">other</span><span class="special">),</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">end</span><span class="special">(</span><span class="identifier">other</span><span class="special">))</span>
<span class="special">{</span>
<span class="special">}</span>
<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Iterator</span><span class="special">&gt;</span>
<span class="identifier">any_range</span><span class="special">(</span><span class="identifier">Iterator</span> <span class="identifier">first</span><span class="special">,</span> <span class="identifier">Iterator</span> <span class="identifier">last</span><span class="special">)</span>
<span class="special">:</span> <span class="identifier">base_type</span><span class="special">(</span><span class="identifier">first</span><span class="special">,</span> <span class="identifier">last</span><span class="special">)</span>
<span class="special">{</span>
<span class="special">}</span>
<span class="special">};</span>
</pre>
<p>
</p>
<a name="range.reference.ranges.any_range.definition"></a><h6>
<a name="id756420"></a>
<a class="link" href="any_range.html#range.reference.ranges.any_range.definition">Definition</a>
</h6>
<p>
Defined in header file <code class="computeroutput"><span class="identifier">boost</span><span class="special">/</span><span class="identifier">range</span><span class="special">/</span><span class="identifier">any_range</span><span class="special">.</span><span class="identifier">hpp</span></code>
</p>
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<td align="right"><div class="copyright-footer">Copyright &#169; 2003 -2010 Thorsten Ottosen, Neil Groves<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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