forked from boostorg/range
[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]
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Neil Groves
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doc/html/range/reference/ranges/any_range.html
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<div class="titlepage"><div><div><h4 class="title">
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<a name="range.reference.ranges.any_range"></a><a class="link" href="any_range.html" title="any_range">any_range</a>
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</h4></div></div></div>
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<a name="range.reference.ranges.any_range.description"></a><h6>
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<a name="id754843"></a>
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<a class="link" href="any_range.html#range.reference.ranges.any_range.description">Description</a>
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</h6>
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<p>
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<code class="computeroutput"><span class="identifier">any_range</span></code> is a range that
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has the type information erased hence a <code class="computeroutput"><span class="identifier">any_range</span><span class="special"><</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>
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<span class="identifier">std</span><span class="special">::</span><span class="identifier">ptrdiff_t</span><span class="special">></span></code>
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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"><</span><span class="keyword">int</span><span class="special">></span></code>, a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">list</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span></code> or many other types.
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</p>
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<p>
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The <a href="http://www.artima.com/cppsource/type_erasure.html" target="_top">type
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erasure article</a> covers the motivation and goals of type erasure
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in this context. Clearly my implementation is building upon a lot of prior
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art created by others. Thomas Becker's <code class="computeroutput"><span class="identifier">any_iterator</span></code>
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was a strong influence. Adobe also have an <code class="computeroutput"><span class="identifier">any_iterator</span></code>
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implementation, but this has very tight coupling to other parts of the
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library that precluded it from use in Boost.Range. Early development versions
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of this Range Adaptor directly used Thomas Becker's any_iterator implementation.
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Subsequently I discovered that the heap allocations of this and many other
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implementations cause poor speed performance particularly at the tails
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of the distribution. To solve this required a new design that incorporated
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the embedded buffer optimization.
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</p>
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<p>
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Despite the underlying <code class="computeroutput"><span class="identifier">any_iterator</span></code>
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being the fastest available implementation, the performance overhead of
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<code class="computeroutput"><span class="identifier">any_range</span></code> is still appreciable
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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>,
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<code class="computeroutput"><span class="identifier">advance</span></code>, <code class="computeroutput"><span class="identifier">equal</span></code> etc. Frequently a better design
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choice is to convert to a canonical form.
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</p>
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<p>
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Please see the <a class="link" href="../adaptors/reference/type_erased.html" title="type_erased">type_erased</a>
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for a Range Adaptor that returns <code class="computeroutput"><span class="identifier">any_range</span></code>
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instances.
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</p>
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<a name="range.reference.ranges.any_range.synopsis"></a><h6>
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<a name="id755211"></a>
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<a class="link" href="any_range.html#range.reference.ranges.any_range.synopsis">Synopsis</a>
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</h6>
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<p>
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</p>
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<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span>
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<span class="keyword">class</span> <span class="identifier">Value</span>
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<span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Traversal</span>
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<span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Reference</span>
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<span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Difference</span>
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<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>
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<span class="special">></span>
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<span class="keyword">class</span> <span class="identifier">any_range</span>
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<span class="special">:</span> <span class="keyword">public</span> <span class="identifier">iterator_range</span><span class="special"><</span>
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<span class="identifier">range_detail</span><span class="special">::</span><span class="identifier">any_iterator</span><span class="special"><</span>
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<span class="identifier">Value</span>
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<span class="special">,</span> <span class="identifier">Traversal</span>
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<span class="special">,</span> <span class="identifier">Reference</span>
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<span class="special">,</span> <span class="identifier">Difference</span>
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<span class="special">,</span> <span class="identifier">Buffer</span>
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<span class="special">></span>
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<span class="special">></span>
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<span class="special">{</span>
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<span class="keyword">typedef</span> <span class="identifier">range_detail</span><span class="special">::</span><span class="identifier">any_iterator</span><span class="special"><</span>
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<span class="identifier">Value</span>
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<span class="special">,</span> <span class="identifier">Traversal</span>
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<span class="special">,</span> <span class="identifier">Reference</span>
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<span class="special">,</span> <span class="identifier">Difference</span>
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<span class="special">,</span> <span class="identifier">Buffer</span>
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<span class="special">></span> <span class="identifier">any_iterator_type</span><span class="special">;</span>
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<span class="keyword">typedef</span> <span class="identifier">iterator_range</span><span class="special"><</span><span class="identifier">any_iterator_type</span><span class="special">></span> <span class="identifier">base_type</span><span class="special">;</span>
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<span class="keyword">struct</span> <span class="identifier">enabler</span> <span class="special">{};</span>
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<span class="keyword">struct</span> <span class="identifier">disabler</span> <span class="special">{};</span>
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<span class="keyword">public</span><span class="special">:</span>
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<span class="keyword">typedef</span> <span class="identifier">any_iterator_type</span> <span class="identifier">iterator</span><span class="special">;</span>
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<span class="keyword">typedef</span> <span class="identifier">any_iterator_type</span> <span class="identifier">const_iterator</span><span class="special">;</span>
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<span class="identifier">any_range</span><span class="special">()</span>
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<span class="special">{</span>
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<span class="special">}</span>
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<span class="identifier">any_range</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">any_range</span><span class="special">&</span> <span class="identifier">other</span><span class="special">)</span>
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<span class="special">:</span> <span class="identifier">base_type</span><span class="special">(</span><span class="identifier">other</span><span class="special">)</span>
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<span class="special">{</span>
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<span class="special">}</span>
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<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">WrappedRange</span><span class="special">></span>
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<span class="identifier">any_range</span><span class="special">(</span><span class="identifier">WrappedRange</span><span class="special">&</span> <span class="identifier">wrapped_range</span><span class="special">)</span>
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<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>
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<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>
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<span class="special">{</span>
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<span class="special">}</span>
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<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">WrappedRange</span><span class="special">></span>
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<span class="identifier">any_range</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">WrappedRange</span><span class="special">&</span> <span class="identifier">wrapped_range</span><span class="special">)</span>
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<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>
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<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>
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<span class="special">{</span>
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<span class="special">}</span>
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<span class="keyword">template</span><span class="special"><</span>
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<span class="keyword">class</span> <span class="identifier">OtherValue</span>
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<span class="special">,</span> <span class="keyword">class</span> <span class="identifier">OtherTraversal</span>
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<span class="special">,</span> <span class="keyword">class</span> <span class="identifier">OtherReference</span>
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<span class="special">,</span> <span class="keyword">class</span> <span class="identifier">OtherDifference</span>
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<span class="special">></span>
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<span class="identifier">any_range</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">any_range</span><span class="special"><</span>
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<span class="identifier">OtherValue</span>
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<span class="special">,</span> <span class="identifier">OtherTraversal</span>
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<span class="special">,</span> <span class="identifier">OtherReference</span>
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<span class="special">,</span> <span class="identifier">OtherDifference</span>
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<span class="special">,</span> <span class="identifier">Buffer</span>
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<span class="special">>&</span> <span class="identifier">other</span><span class="special">)</span>
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<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>
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<span class="special">{</span>
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<span class="special">}</span>
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<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Iterator</span><span class="special">></span>
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<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>
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<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>
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<span class="special">{</span>
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<span class="special">}</span>
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<span class="special">};</span>
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</pre>
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<p>
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</p>
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<a name="range.reference.ranges.any_range.definition"></a><h6>
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<a name="id756420"></a>
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<a class="link" href="any_range.html#range.reference.ranges.any_range.definition">Definition</a>
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</h6>
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<p>
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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>
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</p>
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</div>
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<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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<td align="left"></td>
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<td align="right"><div class="copyright-footer">Copyright © 2003 -2010 Thorsten Ottosen, Neil Groves<p>
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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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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