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|  | <title>Iterator Concepts</title> | ||
|  | </head> | ||
|  | <body> | ||
|  | <h1><img src="../../../../boost.png" align="middle" />Iterator Concepts</h1> | ||
|  | <div class="toc" id="toc"></div> | ||
|  | <p>An Iterator is a restricted pointer-like object pointing into a | ||
|  | vector or matrix container.</p> | ||
|  | <h2><a name="indexed_bidirectional_iterator"  | ||
|  | ></a>Indexed Bidirectional Iterator</h2> | ||
|  | <h4>Description</h4> | ||
|  | <p>An Indexed Bidirectional Iterator is an iterator of a container | ||
|  | that can be dereferenced, incremented, decremented and carries | ||
|  | index information.</p> | ||
|  | <h4>Refinement of</h4> | ||
|  | <p>Assignable, Equality Comparable, Default Constructible.</p> | ||
|  | <h4>Associated types</h4> | ||
|  | <table border="1" summary="associated types"> | ||
|  | <tbody> | ||
|  | <tr> | ||
|  | <td>Value type</td> | ||
|  | <td>The type of the value obtained by dereferencing a Indexed | ||
|  | Bidirectional Iterator</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Container type</td> | ||
|  | <td>The type of the container a Indexed Bidirectional Iterator | ||
|  | points into.</td> | ||
|  | </tr> | ||
|  | </tbody> | ||
|  | </table> | ||
|  | <h4>Notation</h4> | ||
|  | <table border="0" summary="notation"> | ||
|  | <tbody> | ||
|  | <tr> | ||
|  | <td><code>I</code></td> | ||
|  | <td>A type that is a model of Indexed Bidirectional Iterator</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td><code>T</code></td> | ||
|  | <td>The value type of <code>I</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td><code>C</code></td> | ||
|  | <td>The container type of <code>I</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td><code>it</code>, <code>itt, it1</code>, <code>it2</code></td> | ||
|  | <td>Objects of type <code>I</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td><code>t</code></td> | ||
|  | <td>Object of type <code>T</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td><code>c</code></td> | ||
|  | <td>Object of type <code>C</code></td> | ||
|  | </tr> | ||
|  | </tbody> | ||
|  | </table> | ||
|  | <h4>Definitions</h4> | ||
|  | <p>A Indexed Bidirectional Iterator may be <i>mutable</i>, meaning | ||
|  | that the values referred to by objects of that type may be | ||
|  | modified, or <i>constant</i> , meaning that they may not. If an | ||
|  | iterator type is mutable, this implies that its value type is a | ||
|  | model of Assignable; the converse, though, is not necessarily | ||
|  | true.</p> | ||
|  | <p>A Indexed Bidirectional Iterator may have a <i>singular</i> | ||
|  | value, meaning that the results of most operations, including | ||
|  | comparison for equality, are undefined. The only operation that is | ||
|  | guaranteed to be supported is assigning a nonsingular iterator to a | ||
|  | singular iterator.</p> | ||
|  | <p>A Indexed Bidirectional Iterator may have a | ||
|  | <i>dereferenceable</i> value, meaning that dereferencing it yields | ||
|  | a well-defined value. Dereferenceable iterators are always | ||
|  | nonsingular, but the converse is not true.</p> | ||
|  | <p>An Indexed Bidirectional Iterator is <i>past-the-end</i> if it | ||
|  | points beyond the last element of a container. Past-the-end values | ||
|  | are nonsingular and nondereferenceable.</p> | ||
|  | <h4>Valid expressions</h4> | ||
|  | <p>In addition to the expressions defined for Assignable, Equality | ||
|  | Comparable and Default Constructible, the following expressions | ||
|  | must be valid.</p> | ||
|  | <table border="1" summary="expressions"> | ||
|  | <tbody> | ||
|  | <tr> | ||
|  | <th>Name</th> | ||
|  | <th>Expression</th> | ||
|  | <th>Type requirements</th> | ||
|  | <th>Return type</th> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Default constructor</td> | ||
|  | <td><code>I it</code></td> | ||
|  | <td> </td> | ||
|  | <td> </td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Dereference</td> | ||
|  | <td><code>*it</code></td> | ||
|  | <td> </td> | ||
|  | <td>Convertible to <code>T</code>.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Dereference assignment</td> | ||
|  | <td><code>*it = t</code></td> | ||
|  | <td><code>I</code> is mutable.</td> | ||
|  | <td> </td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Member access</td> | ||
|  | <td><code>it->m</code></td> | ||
|  | <td><code>T</code> is a type for which <code>t.m</code> is | ||
|  | defined.</td> | ||
|  | <td> </td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Preincrement</td> | ||
|  | <td><code>++ it</code></td> | ||
|  | <td> </td> | ||
|  | <td><code>I &</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Postincrement</td> | ||
|  | <td><code>it ++</code></td> | ||
|  | <td> </td> | ||
|  | <td><code>I</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Predecrement</td> | ||
|  | <td><code>-- it</code></td> | ||
|  | <td> </td> | ||
|  | <td><code>I &</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Postdecrement</td> | ||
|  | <td><code>it --</code></td> | ||
|  | <td> </td> | ||
|  | <td><code>I</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Index</td> | ||
|  | <td><code>it.index ()</code></td> | ||
|  | <td> </td> | ||
|  | <td><code>C::size_type</code></td> | ||
|  | </tr> | ||
|  | </tbody> | ||
|  | </table> | ||
|  | <h4>Expression Semantics</h4> | ||
|  | <p>Semantics of an expression is defined only where it differs | ||
|  | from, or is not defined in, Assignable, Equality Comparable and | ||
|  | Default Constructible.</p> | ||
|  | <table border="1" summary="semantics"> | ||
|  | <tbody> | ||
|  | <tr> | ||
|  | <th>Name</th> | ||
|  | <th>Expression</th> | ||
|  | <th>Precondition</th> | ||
|  | <th>Semantics</th> | ||
|  | <th>Postcondition</th> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Default constructor</td> | ||
|  | <td><code>I it</code></td> | ||
|  | <td> </td> | ||
|  | <td> </td> | ||
|  | <td><code>it</code> is singular.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Dereference</td> | ||
|  | <td><code>*it</code></td> | ||
|  | <td><code>it</code> is dereferenceable.</td> | ||
|  | <td> </td> | ||
|  | <td> </td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Dereference assignment</td> | ||
|  | <td><code>*it = t</code></td> | ||
|  | <td>Same as for <code>*it</code>.</td> | ||
|  | <td> </td> | ||
|  | <td><code>*it</code> is a copy of t.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Member access</td> | ||
|  | <td><code>it->m</code></td> | ||
|  | <td><code>it</code> is dereferenceable.</td> | ||
|  | <td>Equivalent to <code>(*it).m</code></td> | ||
|  | <td> </td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Preincrement</td> | ||
|  | <td><code>++ it</code></td> | ||
|  | <td><code>it</code> is dereferenceable.</td> | ||
|  | <td><code>it</code> is modified to point to the next element.</td> | ||
|  | <td><code>it</code> is dereferenceable or past-the-end. | ||
|  | <code><br /> | ||
|  | &it == &++ it</code>.<br /> | ||
|  | If <code>it1 == it2</code>,<br /> | ||
|  | then <code>++ it1 == ++ it2</code>.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Postincrement</td> | ||
|  | <td><code>it ++</code></td> | ||
|  | <td>Same as for <code>++ it</code>.</td> | ||
|  | <td>Equivalent to<br /> | ||
|  | <code>{<br /> | ||
|  |  I itt = it;<br /> | ||
|  |  ++ it;<br /> | ||
|  |  return itt;<br /> | ||
|  | }</code></td> | ||
|  | <td><code>it</code> is dereferenceable or past-the-end.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Predecrement</td> | ||
|  | <td><code>-- it</code></td> | ||
|  | <td><code>it</code> is dereferenceable or past-the-end.<br /> | ||
|  | There exists a dereferenceable iterator <code>itt</code> such that | ||
|  | <code>it == ++ itt</code>.</td> | ||
|  | <td><code>it</code> is modified to point to the previous | ||
|  | element.</td> | ||
|  | <td><code>it</code> is dereferenceable.<br /> | ||
|  | <code>&it = &-- it</code>.<br /> | ||
|  | If <code>it1 == it2</code>,<br /> | ||
|  | then <code>-- it1 == -- it2</code>.<br /> | ||
|  | If <code>it2</code> is dereferenceable and <code>it1 == | ||
|  | ++it2</code>,<br /> | ||
|  | then <code>--it1 == it2</code>.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Postdecrement</td> | ||
|  | <td><code>it --</code></td> | ||
|  | <td>Same as for -- <code>it</code>.</td> | ||
|  | <td>Equivalent to<br /> | ||
|  | <code>{<br /> | ||
|  |  I itt = it;<br /> | ||
|  |  -- it;<br /> | ||
|  |  return itt;<br /> | ||
|  | }</code></td> | ||
|  | <td><code>it</code> is dereferenceable. </td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Index</td> | ||
|  | <td><code>it.index ()</code></td> | ||
|  | <td><code>it</code> is dereferenceable.</td> | ||
|  | <td><code>it.index () >= 0</code><br /> | ||
|  | and<br /> | ||
|  | <code>it.index () < it ().size ()</code></td> | ||
|  | <td>If <code>it1 == it2</code>,<br /> | ||
|  | then <code>it1.index () == it2.index ()</code>.<br /> | ||
|  | If <code>it1 == it2</code>,<br /> | ||
|  | then <code>it1.index () < (++ it2).index | ||
|  | ()</code>.<br /> | ||
|  | If <code>it1 == it2</code>,<br /> | ||
|  | then <code>it1.index () > (-- it2).index | ||
|  | ()</code>.</td> | ||
|  | </tr> | ||
|  | </tbody> | ||
|  | </table> | ||
|  | <h4>Complexity guarantees</h4> | ||
|  | <p>The complexity of operations on indexed bidirectional iterators | ||
|  | is guaranteed to be amortized constant time.</p> | ||
|  | <h4>Invariants</h4> | ||
|  | <table border="1" summary="invariants"> | ||
|  | <tbody> | ||
|  | <tr> | ||
|  | <td>Identity</td> | ||
|  | <td><code>it1 == it2</code> if and only if <code>&*it1 == | ||
|  | &*it2</code>.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Symmetry of increment and decrement</td> | ||
|  | <td>If <code>it</code> is dereferenceable, then <code>++ it; | ||
|  | --it;</code> is a null operation. Similarly, <code>-- it; ++ | ||
|  | it;</code> is a null operation.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Relation between iterator index and container element | ||
|  | operator</td> | ||
|  | <td>If <code>it</code> is dereferenceable, <code>*it == it () | ||
|  | (it.index ())</code>.</td> | ||
|  | </tr> | ||
|  | </tbody> | ||
|  | </table> | ||
|  | <h4>Models</h4> | ||
|  | <ul> | ||
|  | <li><code>sparse_vector::iterator</code></li> | ||
|  | </ul> | ||
|  | <h2><a name="indexed_random_access_iterator" | ||
|  | ></a>Indexed Random Access Iterator</h2> | ||
|  | <h4>Description</h4> | ||
|  | <p>An Indexed Random Access Iterator is an iterator of a container | ||
|  | that can be dereferenced, moved forward, moved backward and carries | ||
|  | index information.</p> | ||
|  | <h4>Refinement of</h4> | ||
|  | <p>LessThanComparable, <a href= | ||
|  | "#indexed_bidirectional_iterator">Indexed Bidirectional | ||
|  | Iterator</a> .</p> | ||
|  | <h4>Associated types</h4> | ||
|  | <table border="1" summary="associated types"> | ||
|  | <tbody> | ||
|  | <tr> | ||
|  | <td>Value type</td> | ||
|  | <td>The type of the value obtained by dereferencing a Indexed | ||
|  | Random Access Iterator</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Container type</td> | ||
|  | <td>The type of the container a Indexed Random Access Iterator | ||
|  | points into.</td> | ||
|  | </tr> | ||
|  | </tbody> | ||
|  | </table> | ||
|  | <h4>Notation</h4> | ||
|  | <table border="0" summary="notation"> | ||
|  | <tbody> | ||
|  | <tr> | ||
|  | <td><code>I</code></td> | ||
|  | <td>A type that is a model of Indexed Random Access Iterator</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td><code>T</code></td> | ||
|  | <td>The value type of <code>I</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td><code>C</code></td> | ||
|  | <td>The container type of <code>I</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td><code>it</code>, <code>itt, it1</code>, <code>it2</code></td> | ||
|  | <td>Objects of type <code>I</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td><code>t</code></td> | ||
|  | <td>Object of type <code>T</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td><code>n</code></td> | ||
|  | <td>Object of type <code>C::difference_type</code></td> | ||
|  | </tr> | ||
|  | </tbody> | ||
|  | </table> | ||
|  | <h4>Definitions</h4> | ||
|  | <p>An Indexed Random Access Iterator <code>it1</code> is | ||
|  | <i>reachable</i> from an Indexed Random Access Iterator | ||
|  | <code>it2</code> if, after applying <code>operator ++</code> to | ||
|  | <code>it2</code> a finite number of times, <code>it1 == | ||
|  | it2</code>.</p> | ||
|  | <h4>Valid expressions</h4> | ||
|  | <p>In addition to the expressions defined for <a href= | ||
|  | "#indexed_bidirectional_iterator">Indexed Bidirectional | ||
|  | Iterator</a> , the following expressions must be valid.</p> | ||
|  | <table border="1" summary="expressions"> | ||
|  | <tbody> | ||
|  | <tr> | ||
|  | <th>Name</th> | ||
|  | <th>Expression</th> | ||
|  | <th>Type requirements</th> | ||
|  | <th>Return type</th> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Forward motion</td> | ||
|  | <td><code>it += n</code></td> | ||
|  | <td> </td> | ||
|  | <td><code>I &</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Iterator addition</td> | ||
|  | <td><code>it + n</code></td> | ||
|  | <td> </td> | ||
|  | <td><code>I</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Backward motion</td> | ||
|  | <td><code>i -= n</code></td> | ||
|  | <td> </td> | ||
|  | <td><code>I &</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Iterator subtraction</td> | ||
|  | <td><code>it - n</code></td> | ||
|  | <td> </td> | ||
|  | <td><code>I</code> </td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Difference</td> | ||
|  | <td><code>it1 - it2</code></td> | ||
|  | <td> </td> | ||
|  | <td><code>C::difference_type</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Element operator</td> | ||
|  | <td><code>it [n]</code></td> | ||
|  | <td> </td> | ||
|  | <td>Convertible to <code>T</code>.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Element assignment</td> | ||
|  | <td><code>it [n] = t</code></td> | ||
|  | <td><code>I</code> is mutable</td> | ||
|  | <td>Convertible to <code>T</code>.</td> | ||
|  | </tr> | ||
|  | </tbody> | ||
|  | </table> | ||
|  | <h4>Expression Semantics</h4> | ||
|  | <p>Semantics of an expression is defined only where it differs | ||
|  | from, or is not defined in, <a href= | ||
|  | "#indexed_bidirectional_iterator">Indexed Bidirectional | ||
|  | Iterator</a> .</p> | ||
|  | <table border="1" summary="semantics"> | ||
|  | <tbody> | ||
|  | <tr> | ||
|  | <th>Name</th> | ||
|  | <th>Expression</th> | ||
|  | <th>Precondition</th> | ||
|  | <th>Semantics</th> | ||
|  | <th>Postcondition</th> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Forward motion</td> | ||
|  | <td><code>it += n</code></td> | ||
|  | <td>Including <code>it</code> itself, there must be <code>n</code> | ||
|  | dereferenceable or past-the-end iterators following or preceding | ||
|  | <code>it</code>, depending on whether <code>n</code> is positive or | ||
|  | negative.</td> | ||
|  | <td>If <code>n > 0</code>, equivalent to executing <code>++ | ||
|  | it</code> <code>n</code> times. If <code>n < 0</code>, | ||
|  | equivalent to executing <code>-- it</code> <code>n</code> times. If | ||
|  | <code>n == 0</code>, this is a null operation.</td> | ||
|  | <td><code>it</code> is dereferenceable or past-the-end.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Iterator addition</td> | ||
|  | <td><code>it + n</code></td> | ||
|  | <td>Same as for <code>i += n</code>.</td> | ||
|  | <td>Equivalent to<br /> | ||
|  | <code>{<br /> | ||
|  |  I itt = it;<br /> | ||
|  |  return itt += n;<br /> | ||
|  | }</code></td> | ||
|  | <td>Result is dereferenceable or past-the-end.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Backward motion</td> | ||
|  | <td><code>it -= n</code></td> | ||
|  | <td>Including <code>it</code> itself, there must be <code>n</code> | ||
|  | dereferenceable or past-the-end iterators preceding or following | ||
|  | <code>it</code>, depending on whether <code>n</code> is positive or | ||
|  | negative.</td> | ||
|  | <td>Equivalent to <code>it += (-n)</code>.</td> | ||
|  | <td><code>it</code> is dereferenceable or past-the-end.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Iterator subtraction</td> | ||
|  | <td><code>it - n</code></td> | ||
|  | <td>Same as for <code>i -= n</code>.</td> | ||
|  | <td>Equivalent to<br /> | ||
|  | <code>{<br /> | ||
|  |  I itt = it;<br /> | ||
|  |  return itt -= n;<br /> | ||
|  | }</code></td> | ||
|  | <td>Result is dereferenceable or past-the-end.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Difference</td> | ||
|  | <td><code>it1 - it2</code></td> | ||
|  | <td>Either <code>it1</code> is reachable from <code>it2</code> or | ||
|  | <code>it2</code> is reachable from <code>it1</code>, or both.</td> | ||
|  | <td>Returns a number <code>n</code> such that <code>it1 == it2 + | ||
|  | n</code></td> | ||
|  | <td> </td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Element operator</td> | ||
|  | <td><code>it [n]</code></td> | ||
|  | <td><code>it + n</code> exists and is dereferenceable.</td> | ||
|  | <td>Equivalent to <code>*(it + n)</code></td> | ||
|  | <td> </td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Element assignment</td> | ||
|  | <td><code>i[n] = t</code></td> | ||
|  | <td>Same as for <code>it [n]</code>.</td> | ||
|  | <td>Equivalent to <code>*(it + n) = t</code></td> | ||
|  | <td> </td> | ||
|  | </tr> | ||
|  | </tbody> | ||
|  | </table> | ||
|  | <h4>Complexity guarantees</h4> | ||
|  | <p>The complexity of operations on indexed random access iterators | ||
|  | is guaranteed to be amortized constant time.</p> | ||
|  | <h4>Invariants</h4> | ||
|  | <table border="1" summary="invariants"> | ||
|  | <tbody> | ||
|  | <tr> | ||
|  | <td>Symmetry of addition and subtraction</td> | ||
|  | <td>If <code>it + n</code> is well-defined, then <code>it += n; it | ||
|  | -= n;</code> and <code>(it + n) - n</code> are null operations. | ||
|  | Similarly, if <code>it - n</code> is well-defined, then <code>it -= | ||
|  | n; it += n;</code> and <code>(it - n) + n</code> are null | ||
|  | operations.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Relation between distance and addition</td> | ||
|  | <td>If <code>it1 - it2</code> is well-defined, then <code>it1 == | ||
|  | it2 + (it1 - it2)</code>.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Reachability and distance</td> | ||
|  | <td>If <code>it1</code> is reachable from <code>it2</code>, then | ||
|  | <code>it1 - it2 >= 0</code>.</td> | ||
|  | </tr> | ||
|  | </tbody> | ||
|  | </table> | ||
|  | <h4>Models</h4> | ||
|  | <ul> | ||
|  | <li><code>vector::iterator</code></li> | ||
|  | </ul> | ||
|  | <h2><a name="indexed_bidirectional_cr_iterator" | ||
|  | ></a>Indexed Bidirectional Column/Row Iterator</h2> | ||
|  | <h4>Description</h4> | ||
|  | <p>An Indexed Bidirectional Column/Row Iterator is an iterator of a | ||
|  | container that can be dereferenced, incremented, decremented and | ||
|  | carries index information.</p> | ||
|  | <h4>Refinement of</h4> | ||
|  | <p>Assignable, Equality Comparable, Default Constructible.</p> | ||
|  | <h4>Associated types</h4> | ||
|  | <table border="1" summary="associated types"> | ||
|  | <tbody> | ||
|  | <tr> | ||
|  | <td>Value type</td> | ||
|  | <td>The type of the value obtained by dereferencing a Indexed | ||
|  | Bidirectional Column/Row Iterator</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Container type</td> | ||
|  | <td>The type of the container a Indexed Bidirectional Column/Row | ||
|  | Iterator points into.</td> | ||
|  | </tr> | ||
|  | </tbody> | ||
|  | </table> | ||
|  | <h4>Notation</h4> | ||
|  | <table border="0" summary="notation"> | ||
|  | <tbody> | ||
|  | <tr> | ||
|  | <td><code>I1</code></td> | ||
|  | <td>A type that is a model of Indexed Bidirectional Column/Row | ||
|  | Iterator</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td><code>I2</code></td> | ||
|  | <td>A type that is a model of Indexed Bidirectional Row/Column | ||
|  | Iterator</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td><code>T</code></td> | ||
|  | <td>The value type of <code>I1</code> and <code>I2</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td><code>C</code></td> | ||
|  | <td>The container type of <code>I1</code> and <code>I2</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td><code>it1</code>, <code>it1t, it11</code>, | ||
|  | <code>it12</code></td> | ||
|  | <td>Objects of type <code>I1</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td><code>it2</code>, <code>it2t</code></td> | ||
|  | <td>Objects of type <code>I2</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td><code>t</code></td> | ||
|  | <td>Object of type <code>T</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td><code>c</code></td> | ||
|  | <td>Object of type <code>C</code></td> | ||
|  | </tr> | ||
|  | </tbody> | ||
|  | </table> | ||
|  | <h4>Definitions</h4> | ||
|  | <h4>Valid expressions</h4> | ||
|  | <p>In addition to the expressions defined for Assignable, Equality | ||
|  | Comparable and Default Constructible, the following expressions | ||
|  | must be valid.</p> | ||
|  | <table border="1" summary="expressions"> | ||
|  | <tbody> | ||
|  | <tr> | ||
|  | <th>Name</th> | ||
|  | <th>Expression</th> | ||
|  | <th>Type requirements</th> | ||
|  | <th>Return type</th> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Default constructor</td> | ||
|  | <td><code>I1 it</code></td> | ||
|  | <td> </td> | ||
|  | <td> </td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Dereference</td> | ||
|  | <td><code>*it</code></td> | ||
|  | <td> </td> | ||
|  | <td>Convertible to <code>T</code>.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Dereference assignment</td> | ||
|  | <td><code>*it = t</code></td> | ||
|  | <td><code>I1</code> is mutable.</td> | ||
|  | <td> </td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Member access</td> | ||
|  | <td><code>it->m</code></td> | ||
|  | <td><code>T</code> is a type for which <code>t.m</code> is | ||
|  | defined.</td> | ||
|  | <td> </td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Preincrement</td> | ||
|  | <td><code>++ it</code></td> | ||
|  | <td> </td> | ||
|  | <td><code>I1 &</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Postincrement</td> | ||
|  | <td><code>it ++</code></td> | ||
|  | <td> </td> | ||
|  | <td><code>I1</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Predecrement</td> | ||
|  | <td><code>-- it</code></td> | ||
|  | <td> </td> | ||
|  | <td><code>I1 &</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Postdecrement</td> | ||
|  | <td><code>it --</code></td> | ||
|  | <td> </td> | ||
|  | <td><code>I1</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Row Index</td> | ||
|  | <td><code>it.index1 ()</code></td> | ||
|  | <td> </td> | ||
|  | <td><code>C::size_type</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Column Index</td> | ||
|  | <td><code>it.index2 ()</code></td> | ||
|  | <td> </td> | ||
|  | <td><code>C::size_type</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Row/Column Begin</td> | ||
|  | <td><code>it.begin ()</code></td> | ||
|  | <td> </td> | ||
|  | <td><code>I2</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Row/Column End</td> | ||
|  | <td><code>it.end ()</code></td> | ||
|  | <td> </td> | ||
|  | <td><code>I2</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Reverse Row/Column Begin</td> | ||
|  | <td><code>it.rbegin ()</code></td> | ||
|  | <td> </td> | ||
|  | <td><code>reverse_iterator<I2></code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Reverse Row/Column End</td> | ||
|  | <td><code>it.rend ()</code></td> | ||
|  | <td> </td> | ||
|  | <td><code>reverse_iterator<I2></code></td> | ||
|  | </tr> | ||
|  | </tbody> | ||
|  | </table> | ||
|  | <h4>Expression Semantics</h4> | ||
|  | <p>Semantics of an expression is defined only where it differs | ||
|  | from, or is not defined in, Assignable, Equality Comparable and | ||
|  | Default Constructible.</p> | ||
|  | <table border="1" summary="semantics"> | ||
|  | <tbody> | ||
|  | <tr> | ||
|  | <th>Name</th> | ||
|  | <th>Expression</th> | ||
|  | <th>Precondition</th> | ||
|  | <th>Semantics</th> | ||
|  | <th>Postcondition</th> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Default constructor</td> | ||
|  | <td><code>I1 it</code></td> | ||
|  | <td> </td> | ||
|  | <td> </td> | ||
|  | <td><code>it</code> is singular.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Dereference</td> | ||
|  | <td><code>*it</code></td> | ||
|  | <td><code>it</code> is dereferenceable.</td> | ||
|  | <td> </td> | ||
|  | <td> </td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Dereference assignment</td> | ||
|  | <td><code>*it = t</code></td> | ||
|  | <td>Same as for <code>*it</code>.</td> | ||
|  | <td> </td> | ||
|  | <td><code>*it</code> is a copy of t.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Member access</td> | ||
|  | <td><code>it->m</code></td> | ||
|  | <td><code>it</code> is dereferenceable.</td> | ||
|  | <td>Equivalent to <code>(*it).m</code></td> | ||
|  | <td> </td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Preincrement</td> | ||
|  | <td><code>++ it</code></td> | ||
|  | <td><code>it</code> is dereferenceable.</td> | ||
|  | <td><code>it</code> is modified to point to the next element of | ||
|  | the column/row, i.e. for column iterators holds<br /> | ||
|  | <code>it.index1 () < (++ it).index1 ()</code> and<br /> | ||
|  | <code>it.index2 () == (++ it).index2 ()</code>,<br /> | ||
|  | for row iterators holds<br /> | ||
|  | <code>it.index1 () == (++ it).index1 ()</code> and<br /> | ||
|  | <code>it.index2 () < (++ it).index2 ()</code>.<br /></td> | ||
|  | <td><code>it</code> is dereferenceable or past-the-end. | ||
|  | <code><br /> | ||
|  | &it == &++ it</code>.<br /> | ||
|  | If <code>it1 == it2</code>,<br /> | ||
|  | then <code>++ it1 == ++ it2</code>.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Postincrement</td> | ||
|  | <td><code>it ++</code></td> | ||
|  | <td>Same as for <code>++ it</code>.</td> | ||
|  | <td>Equivalent to<br /> | ||
|  | <code>{<br /> | ||
|  |  I1 itt = it;<br /> | ||
|  |  ++ it;<br /> | ||
|  |  return itt;<br /> | ||
|  | }</code></td> | ||
|  | <td><code>it</code> is dereferenceable or past-the-end.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Predecrement</td> | ||
|  | <td><code>-- it</code></td> | ||
|  | <td><code>it</code> is dereferenceable or past-the-end.<br /> | ||
|  | There exists a dereferenceable iterator <code>itt</code> such that | ||
|  | <code>it == ++ itt</code>.</td> | ||
|  | <td><code>it</code> is modified to point to the previous  | ||
|  | element of the column/row, i.e. for column iterators holds<br /> | ||
|  | <code>it.index1 () > (-- it).index1 ()</code> and<br /> | ||
|  | <code>it.index2 () == (-- it).index2 ()</code>,<br /> | ||
|  | for row iterators holds<br /> | ||
|  | <code>it.index1 () == (-- it).index1 ()</code> and<br /> | ||
|  | <code>it.index2 () > (-- it).index2 ()</code>.</td> | ||
|  | <td><code>it</code> is dereferenceable.<br /> | ||
|  | <code>&it = &-- it</code>.<br /> | ||
|  | If <code>it1 == it2</code>,<br /> | ||
|  | then <code>-- it1 == -- it2</code>.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Postdecrement</td> | ||
|  | <td><code>it --</code></td> | ||
|  | <td>Same as for -- <code>it</code>.</td> | ||
|  | <td>Equivalent to<br /> | ||
|  | <code>{<br /> | ||
|  |  I1 itt = it;<br /> | ||
|  |  -- it;<br /> | ||
|  |  return itt;<br /> | ||
|  | }</code></td> | ||
|  | <td><code>it</code> is dereferenceable. </td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Row Index</td> | ||
|  | <td><code>it.index1 ()</code></td> | ||
|  | <td>If <code>it</code> is a Row iterator then <code>it</code> must be dereferenceable.</td> | ||
|  | <td><code>it.index1 () >= 0</code> and<br /> | ||
|  | <code>it.index1 () < it () .size1 ()</code></td> | ||
|  | <td>If <code>it1 == it2</code>,<br /> | ||
|  | then <code>it1.index1 () == 12.index1 ()</code>.<br /> | ||
|  | If <code>it1</code>, <code>it2</code> are Row Iterators with <code>it1 == it2</code>,<br /> | ||
|  | then <code>it1.index1 () < (++ it2</code>).<code>index1 ()</code>.<br /> | ||
|  | and <code>it1.index1 () > (-- it2</code>).<code>index1 ()</code>.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Column Index</td> | ||
|  | <td><code>it.index2 ()</code></td> | ||
|  | <td>If <code>it</code> is a Column iterator then <code>it</code> must be dereferenceable.</td> | ||
|  | <td><code>it.index2 () >= 0</code> and<br /> | ||
|  | <code>it.index2 () < it () .size2 ()</code></td> | ||
|  | <td>If <code>it1 == it2</code>,<br /> | ||
|  | then <code>it1.index2 () == it2</code>.<code>index2 ()</code> | ||
|  | .<br /> | ||
|  | If <code>it1</code>, <code>it2</code> are Column Iterators with <code>it1 == i12</code>,<br /> | ||
|  | then <code>it1.index2 () < (++ it2</code>).<code>index2 ()</code>.<br /> | ||
|  | end <code>it1.index2 () > (-- it2</code>).<code>index2 ()</code>.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Row/Column Begin</td> | ||
|  | <td><code>it.begin ()</code></td> | ||
|  | <td><code>it</code> is dereferenceable.</td> | ||
|  | <td>If <code>it</code> is a Column Iterator,<br /> | ||
|  | then <code>it2 = it.begin ()</code> is a Row Iterator<br /> | ||
|  | with <code>it2.index1 () == it.index1 ()</code>. | ||
|  | <p>If <code>it</code> is a Row Iterator,<br /> | ||
|  | then <code>it2 = it.begin ()</code> is a Column Iterator<br /> | ||
|  | with <code>it2.index2 () == it.index2 ()</code>.</p> | ||
|  | </td> | ||
|  | <td> </td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Row/Column End</td> | ||
|  | <td><code>it.end ()</code></td> | ||
|  | <td><code>it</code> is dereferenceable.</td> | ||
|  | <td>If <code>it</code> is a Column Iterator,<br /> | ||
|  | then <code>it2 = it.end ()</code> is a Row Iterator<br /> | ||
|  | with <code>it2.index1 () == it.index1 ()</code>. | ||
|  | <p>If <code>it</code> is a Row Iterator,<br /> | ||
|  | then <code>it2 = it.end ()</code> is a Column Iterator<br /> | ||
|  | with <code>it2.index2 () == it.index2 ()</code>.</p> | ||
|  | </td> | ||
|  | <td> </td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Reverse Row/Column Begin</td> | ||
|  | <td><code>it.rbegin ()</code></td> | ||
|  | <td><code>it</code> is dereferenceable.</td> | ||
|  | <td>Equivalent to <code>reverse_iterator<I2> (it.end | ||
|  | ())</code>.</td> | ||
|  | <td> </td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Reverse Row/Column End</td> | ||
|  | <td><code>it.rend ()</code></td> | ||
|  | <td><code>it</code> is dereferenceable.</td> | ||
|  | <td>Equivalent to <code>reverse_iterator<I2> (it.begin | ||
|  | ())</code>.</td> | ||
|  | <td> </td> | ||
|  | </tr> | ||
|  | </tbody> | ||
|  | </table> | ||
|  | <h4>Complexity guarantees</h4> | ||
|  | <p>The complexity of operations on indexed bidirectional column/row | ||
|  | iterators is guaranteed to be logarithmic depending on the size of | ||
|  | the container. The complexity of one iterator (depending on the | ||
|  | storage layout) can be lifted to be amortized constant time. The | ||
|  | complexity of the other iterator (depending on the storage layout | ||
|  | and the container) can be lifted to be amortized constant time for | ||
|  | the first row/first column respectively.</p> | ||
|  | <h4>Invariants</h4> | ||
|  | <table border="1" summary="invariants"> | ||
|  | <tbody> | ||
|  | <tr> | ||
|  | <td>Identity</td> | ||
|  | <td><code>it1 == it2</code> if and only if <code>&*it1 == | ||
|  | &*it2</code>.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Symmetry of increment and decrement</td> | ||
|  | <td>If <code>it</code> is dereferenceable, then <code>++ it; | ||
|  | --it;</code> is a null operation. Similarly, <code>-- it; ++ | ||
|  | it;</code> is a null operation.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Relation between iterator index and container element | ||
|  | operator</td> | ||
|  | <td>If <code>it</code> is dereferenceable, <code>*it == it () | ||
|  | (it.index1 (), it.index2 ())</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Relation between iterator column/row begin and iterator | ||
|  | index</td> | ||
|  | <td>If <code>it</code> is a Column Iterator | ||
|  | and <code>it2 = it.begin ()</code> then <code>it2.index2 () < | ||
|  | it2t.index2 ()</code> for all <code>it2t</code> with <code>it2t () | ||
|  | == it2 ()</code> and <code>it2t ().index1 () == it2 ().index1 | ||
|  | ()</code>. | ||
|  | <p>If <code>it</code> is a Row Iterator and | ||
|  | <code>it2 = it.begin ()</code> then <code>it2.index1 () < | ||
|  | it2t.index1 ()</code> for all <code>it2t</code> with <code>it2t () | ||
|  | == it2 ()</code> and <code>it2t ().index2 () == it2 ().index2 | ||
|  | ()</code>.</p> | ||
|  | </td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Relation between iterator column/row end and iterator | ||
|  | index</td> | ||
|  | <td>If <code>it</code> is a Column Iterator | ||
|  | and <code>it2 = it.end ()</code> then <code>it2.index2 () > | ||
|  | it2t.index2 ()</code> for all <code>it2t</code> with <code>it2t () | ||
|  | == it2 ()</code> and <code>it2t ().index1 () == it2 ().index1 | ||
|  | ()</code>. | ||
|  | <p>If <code>it</code> is a Row Iterator and | ||
|  | <code>it2 = it.end ()</code> then <code>it2.index1 () > | ||
|  | it2t.index1 ()</code> for all <code>it2t</code> with <code>it2t () | ||
|  | == it2 ()</code> and <code>it2t ().index2 () == it2 ().index2 | ||
|  | ()</code>.</p> | ||
|  | </td> | ||
|  | </tr> | ||
|  | </tbody> | ||
|  | </table> | ||
|  | <h4>Models</h4> | ||
|  | <ul> | ||
|  | <li><code>sparse_matrix::iterator1</code></li> | ||
|  | <li><code>sparse_matrix::iterator2</code></li> | ||
|  | </ul> | ||
|  | <h2><a name="indexed_random_access_cr_iterator" | ||
|  | ></a>Indexed Random Access Column/Row Iterator</h2> | ||
|  | <h4>Description</h4> | ||
|  | <p>An Indexed Random Access Column/Row Iterator is an iterator of a | ||
|  | container that can be dereferenced, incremented, decremented and | ||
|  | carries index information.</p> | ||
|  | <h4>Refinement of</h4> | ||
|  | <p><a href="#indexed_bidirectional_cr_iterator">Indexed | ||
|  | Bidirectional Column/Row Iterator</a> .</p> | ||
|  | <h4>Associated types</h4> | ||
|  | <table border="1" summary="associated types"> | ||
|  | <tbody> | ||
|  | <tr> | ||
|  | <td>Value type</td> | ||
|  | <td>The type of the value obtained by dereferencing a Indexed | ||
|  | Random Access Column/Row Iterator</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Container type</td> | ||
|  | <td>The type of the container a Indexed Random Access Column/Row | ||
|  | Iterator points into.</td> | ||
|  | </tr> | ||
|  | </tbody> | ||
|  | </table> | ||
|  | <h4>Notation</h4> | ||
|  | <table border="0" summary="notation"> | ||
|  | <tbody> | ||
|  | <tr> | ||
|  | <td><code>I</code></td> | ||
|  | <td>A type that is a model of Indexed Random Access Column/Row | ||
|  | Iterator</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td><code>T</code></td> | ||
|  | <td>The value type of <code>I</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td><code>C</code></td> | ||
|  | <td>The container type of <code>I</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td><code>it</code>, <code>itt, it1</code>, <code>it2</code></td> | ||
|  | <td>Objects of type <code>I</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td><code>t</code></td> | ||
|  | <td>Object of type <code>T</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td><code>c</code></td> | ||
|  | <td>Object of type <code>C</code></td> | ||
|  | </tr> | ||
|  | </tbody> | ||
|  | </table> | ||
|  | <h4>Definitions</h4> | ||
|  | <h4>Valid expressions</h4> | ||
|  | <p>In addition to the expressions defined for <a href= | ||
|  | "#indexed_bidirectional_cr_iterator">Indexed Bidirectional | ||
|  | Column/Row Iterator</a> , the following expressions must be | ||
|  | valid.</p> | ||
|  | <table border="1" summary="expressions"> | ||
|  | <tbody> | ||
|  | <tr> | ||
|  | <th>Name</th> | ||
|  | <th>Expression</th> | ||
|  | <th>Type requirements</th> | ||
|  | <th>Return type</th> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Forward motion</td> | ||
|  | <td><code>it += n</code></td> | ||
|  | <td> </td> | ||
|  | <td><code>I &</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Iterator addition</td> | ||
|  | <td><code>it + n</code></td> | ||
|  | <td> </td> | ||
|  | <td><code>I</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Backward motion</td> | ||
|  | <td><code>i -= n</code></td> | ||
|  | <td> </td> | ||
|  | <td><code>I &</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Iterator subtraction</td> | ||
|  | <td><code>it - n</code></td> | ||
|  | <td> </td> | ||
|  | <td><code>I</code> </td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Difference</td> | ||
|  | <td><code>it1 - it2</code></td> | ||
|  | <td> </td> | ||
|  | <td><code>C::difference_type</code></td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Element operator</td> | ||
|  | <td><code>it [n]</code></td> | ||
|  | <td> </td> | ||
|  | <td>Convertible to <code>T</code>.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Element assignment</td> | ||
|  | <td><code>it [n] = t</code></td> | ||
|  | <td><code>I</code> is mutable</td> | ||
|  | <td>Convertible to <code>T</code>.</td> | ||
|  | </tr> | ||
|  | </tbody> | ||
|  | </table> | ||
|  | <h4>Expression Semantics</h4> | ||
|  | <p>Semantics of an expression is defined only where it differs | ||
|  | from, or is not defined in, <a href= | ||
|  | "#indexed_bidirectional_cr_iterator">Indexed Bidirectional | ||
|  | Column/Row Iterator</a> .</p> | ||
|  | <table border="1" summary="semantics"> | ||
|  | <tbody> | ||
|  | <tr> | ||
|  | <th>Name</th> | ||
|  | <th>Expression</th> | ||
|  | <th>Precondition</th> | ||
|  | <th>Semantics</th> | ||
|  | <th>Postcondition</th> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Forward motion</td> | ||
|  | <td><code>it += n</code></td> | ||
|  | <td>Including <code>it</code> itself, there must be <code>n</code> | ||
|  | dereferenceable or past-the-end iterators following or preceding | ||
|  | <code>it</code>, depending on whether <code>n</code> is positive or | ||
|  | negative.</td> | ||
|  | <td>If <code>n > 0</code>, equivalent to executing <code>++ | ||
|  | it</code> <code>n</code> times. If <code>n < 0</code>, | ||
|  | equivalent to executing <code>-- it</code> <code>n</code> times. If | ||
|  | <code>n == 0</code>, this is a null operation.</td> | ||
|  | <td><code>it</code> is dereferenceable or past-the-end.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Iterator addition</td> | ||
|  | <td><code>it + n</code></td> | ||
|  | <td>Same as for <code>i += n</code>.</td> | ||
|  | <td>Equivalent to<br /> | ||
|  | <code>{<br /> | ||
|  |  I itt = it;<br /> | ||
|  |  return itt += n;<br /> | ||
|  | }</code></td> | ||
|  | <td>Result is dereferenceable or past-the-end.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Backward motion</td> | ||
|  | <td><code>it -= n</code></td> | ||
|  | <td>Including <code>it</code> itself, there must be <code>n</code> | ||
|  | dereferenceable or past-the-end iterators preceding or following | ||
|  | <code>it</code>, depending on whether <code>n</code> is positive or | ||
|  | negative.</td> | ||
|  | <td>Equivalent to <code>it += (-n)</code>.</td> | ||
|  | <td><code>it</code> is dereferenceable or past-the-end.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Iterator subtraction</td> | ||
|  | <td><code>it - n</code></td> | ||
|  | <td>Same as for <code>i -= n</code>.</td> | ||
|  | <td>Equivalent to<br /> | ||
|  | <code>{<br /> | ||
|  |  I itt = it;<br /> | ||
|  |  return itt -= n;<br /> | ||
|  | }</code></td> | ||
|  | <td>Result is dereferenceable or past-the-end.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Difference</td> | ||
|  | <td><code>it1 - it2</code></td> | ||
|  | <td>Either <code>it1</code> is reachable from <code>it2</code> or | ||
|  | <code>it2</code> is reachable from <code>it1</code>, or both.</td> | ||
|  | <td>Returns a number <code>n</code> such that <code>it1 == it2 + | ||
|  | n</code></td> | ||
|  | <td> </td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Element operator</td> | ||
|  | <td><code>it [n]</code></td> | ||
|  | <td><code>it + n</code> exists and is dereferenceable.</td> | ||
|  | <td>Equivalent to <code>*(it + n)</code></td> | ||
|  | <td> </td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Element assignment</td> | ||
|  | <td><code>i[n] = t</code></td> | ||
|  | <td>Same as for <code>it [n]</code>.</td> | ||
|  | <td>Equivalent to <code>*(it + n) = t</code></td> | ||
|  | <td> </td> | ||
|  | </tr> | ||
|  | </tbody> | ||
|  | </table> | ||
|  | <h4>Complexity guarantees</h4> | ||
|  | <p>The complexity of operations on indexed random access Column/Row | ||
|  | iterators is guaranteed to be amortized constant time.</p> | ||
|  | <h4>Invariants</h4> | ||
|  | <table border="1" summary="invariants"> | ||
|  | <tbody> | ||
|  | <tr> | ||
|  | <td>Symmetry of addition and subtraction</td> | ||
|  | <td>If <code>it + n</code> is well-defined, then <code>it += n; it | ||
|  | -= n;</code> and <code>(it + n) - n</code> are null operations. | ||
|  | Similarly, if <code>it - n</code> is well-defined, then <code>it -= | ||
|  | n; it += n;</code> and <code>(it - n) + n</code> are null | ||
|  | operations.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Relation between distance and addition</td> | ||
|  | <td>If <code>it1 - it2</code> is well-defined, then <code>it1 == | ||
|  | it2 + (it1 - it2)</code>.</td> | ||
|  | </tr> | ||
|  | <tr> | ||
|  | <td>Reachability and distance</td> | ||
|  | <td>If <code>it1</code> is reachable from <code>it2</code>, then | ||
|  | <code>it1 - it2 >= 0</code>.</td> | ||
|  | </tr> | ||
|  | </tbody> | ||
|  | </table> | ||
|  | <h4>Models</h4> | ||
|  | <ul> | ||
|  | <li><code>matrix::iterator1</code></li> | ||
|  | <li><code>matrix::iterator2</code></li> | ||
|  | </ul> | ||
|  | <hr /> | ||
|  | <p>Copyright (©) 2000-2002 Joerg Walter, Mathias Koch<br /> | ||
|  |    Use, modification and distribution are subject to 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"> | ||
|  |       http://www.boost.org/LICENSE_1_0.txt | ||
|  |    </a>). | ||
|  | </p> | ||
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