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added Interoperable Iterators
[SVN r21698]
This commit is contained in:
Jeremy Siek
@ -81,15 +81,16 @@ of iterators that are used in practice.</td>
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<li><a class="reference" href="#forward-traversal-iterators-lib-forward-traversal-iterators" id="id18" name="id18">Forward Traversal Iterators [lib.forward.traversal.iterators]</a></li>
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<li><a class="reference" href="#bidirectional-traversal-iterators-lib-bidirectional-traversal-iterators" id="id19" name="id19">Bidirectional Traversal Iterators [lib.bidirectional.traversal.iterators]</a></li>
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<li><a class="reference" href="#random-access-traversal-iterators-lib-random-access-traversal-iterators" id="id20" name="id20">Random Access Traversal Iterators [lib.random.access.traversal.iterators]</a></li>
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<li><a class="reference" href="#interoperable-iterators-lib-interoperable-iterators" id="id21" name="id21">Interoperable Iterators [lib.interoperable.iterators]</a></li>
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</ul>
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</li>
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</ul>
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</li>
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<li><a class="reference" href="#addition-to-lib-iterator-synopsis" id="id21" name="id21">Addition to [lib.iterator.synopsis]</a></li>
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<li><a class="reference" href="#addition-to-lib-iterator-traits" id="id22" name="id22">Addition to [lib.iterator.traits]</a></li>
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<li><a class="reference" href="#addition-to-lib-iterator-synopsis" id="id22" name="id22">Addition to [lib.iterator.synopsis]</a></li>
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<li><a class="reference" href="#addition-to-lib-iterator-traits" id="id23" name="id23">Addition to [lib.iterator.traits]</a></li>
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</ul>
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</li>
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<li><a class="reference" href="#footnotes" id="id23" name="id23">Footnotes</a></li>
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<li><a class="reference" href="#footnotes" id="id24" name="id24">Footnotes</a></li>
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</ul>
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</div>
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<div class="section" id="motivation">
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@ -311,6 +312,12 @@ position comparison such as <tt class="literal"><span class="pre">operator==</sp
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reason for the fine grain slicing of the concepts into the
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Incrementable and Single Pass is to provide concepts that are exact
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matches with the original input and output iterator requirements.</p>
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<p>This proposal also includes a concept for specifying when an iterator
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is interoperable with another iterator, in the sense that <tt class="literal"><span class="pre">int*</span></tt> is
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interoperable with <tt class="literal"><span class="pre">int</span> <span class="pre">const*</span></tt>.</p>
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<ul class="simple">
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<li>Interoperable Iterators</li>
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</ul>
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<p>The relationship between the new iterator concepts and the old are
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given in the following diagram.</p>
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<p><img alt="oldeqnew.png" src="oldeqnew.png" /></p>
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@ -816,10 +823,144 @@ ordering relation</td>
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<!-- TR1: random_access_traversal_iterator_tag changed to
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random_access_traversal_tag for consistency -->
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</div>
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<div class="section" id="interoperable-iterators-lib-interoperable-iterators">
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<h4><a class="toc-backref" href="#id21" name="interoperable-iterators-lib-interoperable-iterators">Interoperable Iterators [lib.interoperable.iterators]</a></h4>
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<p>A class or built-in type <tt class="literal"><span class="pre">X</span></tt> that models Single Pass Iterator is
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<em>interoperable with</em> a class or built-in type <tt class="literal"><span class="pre">Y</span></tt> that also models
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Single Pass Iterator if both <tt class="literal"><span class="pre">X</span></tt> and <tt class="literal"><span class="pre">Y</span></tt> have the same difference
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type and traversal tag and if the following expressions are valid and
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respect the stated semantics. In the tables below, <tt class="literal"><span class="pre">x</span></tt> is an object
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of type <tt class="literal"><span class="pre">X</span></tt>, <tt class="literal"><span class="pre">y</span></tt> is an object of type <tt class="literal"><span class="pre">Y</span></tt>, <tt class="literal"><span class="pre">Distance</span></tt> is
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<tt class="literal"><span class="pre">iterator_traits<X>::difference_type</span></tt>, and <tt class="literal"><span class="pre">n</span></tt> represents a
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constant object of type <tt class="literal"><span class="pre">Distance</span></tt>.</p>
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<p>If the traversal tag for <tt class="literal"><span class="pre">X</span></tt> and <tt class="literal"><span class="pre">Y</span></tt> is convertible to
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<tt class="literal"><span class="pre">single_pass_traversal_tag</span></tt> then the following requirements must be
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met.</p>
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<table border class="table">
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<colgroup>
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<col width="30%" />
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<col width="34%" />
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<col width="36%" />
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</colgroup>
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<thead valign="bottom">
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<tr><th>Expression</th>
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<th>Return Type</th>
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<th>Assertion/Precondition/Postcondition</th>
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</tr>
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</thead>
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<tbody valign="top">
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<tr><td><tt class="literal"><span class="pre">y</span> <span class="pre">=</span> <span class="pre">x</span></tt></td>
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<td><tt class="literal"><span class="pre">Y</span></tt></td>
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<td>post: <tt class="literal"><span class="pre">y</span> <span class="pre">==</span> <span class="pre">x</span></tt></td>
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</tr>
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<tr><td><tt class="literal"><span class="pre">x</span> <span class="pre">==</span> <span class="pre">y</span></tt></td>
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<td>convertible to <tt class="literal"><span class="pre">bool</span></tt></td>
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<td><tt class="literal"><span class="pre">==</span></tt> is an equivalence relation over its domain.</td>
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</tr>
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<tr><td><tt class="literal"><span class="pre">y</span> <span class="pre">==</span> <span class="pre">x</span></tt></td>
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<td>convertible to <tt class="literal"><span class="pre">bool</span></tt></td>
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<td><tt class="literal"><span class="pre">==</span></tt> is an equivalence relation over its domain.</td>
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</tr>
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<tr><td><tt class="literal"><span class="pre">x</span> <span class="pre">!=</span> <span class="pre">y</span></tt></td>
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<td>convertible to <tt class="literal"><span class="pre">bool</span></tt></td>
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<td><tt class="literal"><span class="pre">bool(a==b)</span> <span class="pre">!=</span> <span class="pre">bool(a!=b)</span></tt> over its domain.</td>
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</tr>
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<tr><td><tt class="literal"><span class="pre">y</span> <span class="pre">!=</span> <span class="pre">x</span></tt></td>
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<td>convertible to <tt class="literal"><span class="pre">bool</span></tt></td>
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<td><tt class="literal"><span class="pre">bool(a==b)</span> <span class="pre">!=</span> <span class="pre">bool(a!=b)</span></tt> over its domain.</td>
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</tr>
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</tbody>
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</table>
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<p>If the traversal tag for <tt class="literal"><span class="pre">X</span></tt> and <tt class="literal"><span class="pre">Y</span></tt> is convertible to
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<tt class="literal"><span class="pre">random_access_traversal_tag</span></tt> then the following requirements must
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be met.</p>
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<table border class="table">
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<colgroup>
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<col width="31%" />
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<col width="35%" />
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<col width="18%" />
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<col width="16%" />
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</colgroup>
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<thead valign="bottom">
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<tr><th>Expression</th>
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<th>Return Type</th>
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<th>Operational Semantics</th>
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<th>Assertion/
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Precondition</th>
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</tr>
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</thead>
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<tbody valign="top">
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<tr><td><tt class="literal"><span class="pre">x</span> <span class="pre"><</span> <span class="pre">y</span></tt></td>
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<td>convertible to <tt class="literal"><span class="pre">bool</span></tt></td>
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<td><tt class="literal"><span class="pre">y</span> <span class="pre">-</span> <span class="pre">x</span> <span class="pre">></span> <span class="pre">0</span></tt></td>
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<td><tt class="literal"><span class="pre"><</span></tt> is a total
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ordering relation</td>
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</tr>
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<tr><td><tt class="literal"><span class="pre">y</span> <span class="pre"><</span> <span class="pre">x</span></tt></td>
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<td>convertible to <tt class="literal"><span class="pre">bool</span></tt></td>
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<td><tt class="literal"><span class="pre">x</span> <span class="pre">-</span> <span class="pre">y</span> <span class="pre">></span> <span class="pre">0</span></tt></td>
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<td><tt class="literal"><span class="pre"><</span></tt> is a total
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ordering relation</td>
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</tr>
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<tr><td><tt class="literal"><span class="pre">x</span> <span class="pre">></span> <span class="pre">y</span></tt></td>
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<td>convertible to <tt class="literal"><span class="pre">bool</span></tt></td>
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<td><tt class="literal"><span class="pre">y</span> <span class="pre"><</span> <span class="pre">x</span></tt></td>
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<td><tt class="literal"><span class="pre">></span></tt> is a total
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ordering relation</td>
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</tr>
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<tr><td><tt class="literal"><span class="pre">y</span> <span class="pre">></span> <span class="pre">x</span></tt></td>
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<td>convertible to <tt class="literal"><span class="pre">bool</span></tt></td>
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<td><tt class="literal"><span class="pre">x</span> <span class="pre"><</span> <span class="pre">y</span></tt></td>
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<td><tt class="literal"><span class="pre">></span></tt> is a total
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ordering relation</td>
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</tr>
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<tr><td><tt class="literal"><span class="pre">x</span> <span class="pre">>=</span> <span class="pre">y</span></tt></td>
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<td>convertible to <tt class="literal"><span class="pre">bool</span></tt></td>
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<td><tt class="literal"><span class="pre">!(x</span> <span class="pre"><</span> <span class="pre">y)</span></tt></td>
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<td> </td>
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</tr>
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<tr><td><tt class="literal"><span class="pre">y</span> <span class="pre">>=</span> <span class="pre">x</span></tt></td>
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<td>convertible to <tt class="literal"><span class="pre">bool</span></tt></td>
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<td><tt class="literal"><span class="pre">!(y</span> <span class="pre"><</span> <span class="pre">x)</span></tt></td>
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<td> </td>
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</tr>
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<tr><td><tt class="literal"><span class="pre">x</span> <span class="pre"><=</span> <span class="pre">y</span></tt></td>
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<td>convertible to <tt class="literal"><span class="pre">bool</span></tt></td>
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<td><tt class="literal"><span class="pre">!(x</span> <span class="pre">></span> <span class="pre">y)</span></tt></td>
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<td> </td>
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</tr>
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<tr><td><tt class="literal"><span class="pre">y</span> <span class="pre"><=</span> <span class="pre">x</span></tt></td>
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<td>convertible to <tt class="literal"><span class="pre">bool</span></tt></td>
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<td><tt class="literal"><span class="pre">!(y</span> <span class="pre">></span> <span class="pre">x)</span></tt></td>
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<td> </td>
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</tr>
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<tr><td><tt class="literal"><span class="pre">y</span> <span class="pre">-</span> <span class="pre">x</span></tt></td>
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<td><tt class="literal"><span class="pre">Distance</span></tt></td>
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<td><tt class="literal"><span class="pre">x</span> <span class="pre"><</span> <span class="pre">y</span> <span class="pre">?</span> <span class="pre">distance(x,y)</span>
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<span class="pre">:</span> <span class="pre">-distance(y,x)</span></tt></td>
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<td>pre: there exists a
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value <tt class="literal"><span class="pre">n</span></tt> of
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<tt class="literal"><span class="pre">Distance</span></tt> such that
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<tt class="literal"><span class="pre">x</span> <span class="pre">+</span> <span class="pre">n</span> <span class="pre">==</span> <span class="pre">y</span></tt>. <tt class="literal"><span class="pre">y</span>
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<span class="pre">==</span> <span class="pre">x</span> <span class="pre">+</span> <span class="pre">(y</span> <span class="pre">-</span> <span class="pre">x)</span></tt>.</td>
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</tr>
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<tr><td><tt class="literal"><span class="pre">x</span> <span class="pre">-</span> <span class="pre">y</span></tt></td>
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<td><tt class="literal"><span class="pre">Distance</span></tt></td>
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<td><tt class="literal"><span class="pre">y</span> <span class="pre"><</span> <span class="pre">x</span> <span class="pre">?</span> <span class="pre">distance(y,x)</span>
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<span class="pre">:</span> <span class="pre">-distance(x,y)</span></tt></td>
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<td>pre: there exists a
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value <tt class="literal"><span class="pre">n</span></tt> of
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<tt class="literal"><span class="pre">Distance</span></tt> such that
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<tt class="literal"><span class="pre">y</span> <span class="pre">+</span> <span class="pre">n</span> <span class="pre">==</span> <span class="pre">x</span></tt>. <tt class="literal"><span class="pre">x</span>
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<span class="pre">==</span> <span class="pre">y</span> <span class="pre">+</span> <span class="pre">(x</span> <span class="pre">-</span> <span class="pre">y)</span></tt>.</td>
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</tr>
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</tbody>
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</table>
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</div>
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</div>
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</div>
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<div class="section" id="addition-to-lib-iterator-synopsis">
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<h2><a class="toc-backref" href="#id21" name="addition-to-lib-iterator-synopsis">Addition to [lib.iterator.synopsis]</a></h2>
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<h2><a class="toc-backref" href="#id22" name="addition-to-lib-iterator-synopsis">Addition to [lib.iterator.synopsis]</a></h2>
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<pre class="literal-block">
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// lib.iterator.traits, traits and tags
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template <class Iterator> struct is_readable_iterator;
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@ -833,7 +974,7 @@ struct random_access_traversal_tag : bidirectional_traversal_tag { };
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</pre>
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</div>
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<div class="section" id="addition-to-lib-iterator-traits">
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<h2><a class="toc-backref" href="#id22" name="addition-to-lib-iterator-traits">Addition to [lib.iterator.traits]</a></h2>
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<h2><a class="toc-backref" href="#id23" name="addition-to-lib-iterator-traits">Addition to [lib.iterator.traits]</a></h2>
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<p>The <tt class="literal"><span class="pre">is_readable_iterator</span></tt> and <tt class="literal"><span class="pre">iterator_traversal</span></tt> class
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templates satisfy the <a class="reference" href="http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/papers/2003/n1519.htm">UnaryTypeTrait</a> requirements.</p>
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<p>Given an iterator type <tt class="literal"><span class="pre">X</span></tt>, <tt class="literal"><span class="pre">is_readable_iterator<X>::value</span></tt>
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@ -862,7 +1003,7 @@ traversal-category(X) =
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</div>
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</div>
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<div class="section" id="footnotes">
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<h1><a class="toc-backref" href="#id23" name="footnotes">Footnotes</a></h1>
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<h1><a class="toc-backref" href="#id24" name="footnotes">Footnotes</a></h1>
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<p>The UnaryTypeTrait concept is defined in <a class="reference" href="http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/papers/2003/n1519.htm">n1519</a>; the LWG added the
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requirement that specializations are derived from their nested
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<tt class="literal"><span class="pre">::type</span></tt>.</p>
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@ -878,7 +1019,7 @@ LocalWords: TraversalTag typename lvalues DWA Hmm JGS mis enum -->
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<hr class="footer" />
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<div class="footer">
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<a class="reference" href="new-iter-concepts.rst">View document source</a>.
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Generated on: 2004-01-13 14:26 UTC.
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Generated on: 2004-01-13 19:20 UTC.
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Generated by <a class="reference" href="http://docutils.sourceforge.net/">Docutils</a> from <a class="reference" href="http://docutils.sourceforge.net/rst.html">reStructuredText</a> source.
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</div>
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</body>
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