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  26 <div class="titlepage"><div><div><h3 class="title">
  27 <a name="the_boost_algorithm_library.CXX11.is_sorted"></a><a class="link" href="is_sorted.html" title="is_sorted">is_sorted
  28       </a>
  29 </h3></div></div></div>
  30 <p>
  31         The header file <code class="computeroutput"><span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">algorithm</span><span class="special">/</span><span class="identifier">cxx11</span><span class="special">/</span><span class="identifier">is_sorted</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
  32         contains functions for determining if a sequence is ordered.
  33       </p>
  34 <h5>
  35 <a name="the_boost_algorithm_library.CXX11.is_sorted.h0"></a>
  36         <span class="phrase"><a name="the_boost_algorithm_library.CXX11.is_sorted.is_sorted"></a></span><a class="link" href="is_sorted.html#the_boost_algorithm_library.CXX11.is_sorted.is_sorted">is_sorted</a>
  37       </h5>
  38 <p>
  39         The function <code class="computeroutput"><span class="identifier">is_sorted</span><span class="special">(</span><span class="identifier">sequence</span><span class="special">)</span></code>
  40         determines whether or not a sequence is completely sorted according so some
  41         criteria. If no comparison predicate is specified, then <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">less</span></code>
  42         is used (i.e, the test is to see if the sequence is non-decreasing)
  43       </p>
  44 <p>
  45 </p>
  46 <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">algorithm</span> <span class="special">{</span>
  47         <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">ForwardIterator</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Pred</span><span class="special">&gt;</span>
  48         <span class="keyword">bool</span> <span class="identifier">is_sorted</span> <span class="special">(</span> <span class="identifier">ForwardIterator</span> <span class="identifier">first</span><span class="special">,</span> <span class="identifier">ForwardIterator</span> <span class="identifier">last</span><span class="special">,</span> <span class="identifier">Pred</span> <span class="identifier">p</span> <span class="special">);</span>
  49
  50         <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">ForwardIterator</span><span class="special">&gt;</span>
  51         <span class="keyword">bool</span> <span class="identifier">is_sorted</span> <span class="special">(</span> <span class="identifier">ForwardIterator</span> <span class="identifier">first</span><span class="special">,</span> <span class="identifier">ForwardIterator</span> <span class="identifier">last</span> <span class="special">);</span>
  52
  53
  54         <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Range</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Pred</span><span class="special">&gt;</span>
  55         <span class="keyword">bool</span> <span class="identifier">is_sorted</span> <span class="special">(</span> <span class="keyword">const</span> <span class="identifier">Range</span> <span class="special">&amp;</span><span class="identifier">r</span><span class="special">,</span> <span class="identifier">Pred</span> <span class="identifier">p</span> <span class="special">);</span>
  56
  57         <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Range</span><span class="special">&gt;</span>
  58         <span class="keyword">bool</span> <span class="identifier">is_sorted</span> <span class="special">(</span> <span class="keyword">const</span> <span class="identifier">Range</span> <span class="special">&amp;</span><span class="identifier">r</span> <span class="special">);</span>
  59 <span class="special">}}</span>
  60 </pre>
  61 <p>
  62       </p>
  63 <p>
  64         Iterator requirements: The <code class="computeroutput"><span class="identifier">is_sorted</span></code>
  65         functions will work forward iterators or better.
  66       </p>
  67 <h5>
  68 <a name="the_boost_algorithm_library.CXX11.is_sorted.h1"></a>
  69         <span class="phrase"><a name="the_boost_algorithm_library.CXX11.is_sorted.is_sorted_until"></a></span><a class="link" href="is_sorted.html#the_boost_algorithm_library.CXX11.is_sorted.is_sorted_until">is_sorted_until</a>
  70       </h5>
  71 <p>
  72         If <code class="computeroutput"><span class="identifier">distance</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">&lt;</span> <span class="number">2</span></code>, then
  73         <code class="computeroutput"><span class="identifier">is_sorted</span> <span class="special">(</span>
  74         <span class="identifier">first</span><span class="special">,</span>
  75         <span class="identifier">last</span> <span class="special">)</span></code>
  76         returns <code class="computeroutput"><span class="identifier">last</span></code>. Otherwise,
  77         it returns the last iterator i in [first,last] for which the range [first,i)
  78         is sorted.
  79       </p>
  80 <p>
  81         In short, it returns the element in the sequence that is "out of order".
  82         If the entire sequence is sorted (according to the predicate), then it will
  83         return <code class="computeroutput"><span class="identifier">last</span></code>.
  84       </p>
  85 <p>
  86 </p>
  87 <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">algorithm</span> <span class="special">{</span>
  88         <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">ForwardIterator</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Pred</span><span class="special">&gt;</span>
  89         <span class="identifier">FI</span> <span class="identifier">is_sorted_until</span> <span class="special">(</span> <span class="identifier">ForwardIterator</span> <span class="identifier">first</span><span class="special">,</span> <span class="identifier">ForwardIterator</span> <span class="identifier">last</span><span class="special">,</span> <span class="identifier">Pred</span> <span class="identifier">p</span> <span class="special">);</span>
  90
  91         <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">ForwardIterator</span><span class="special">&gt;</span>
  92         <span class="identifier">ForwardIterator</span> <span class="identifier">is_sorted_until</span> <span class="special">(</span> <span class="identifier">ForwardIterator</span> <span class="identifier">first</span><span class="special">,</span> <span class="identifier">ForwardIterator</span> <span class="identifier">last</span> <span class="special">);</span>
  93
  94
  95         <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Range</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Pred</span><span class="special">&gt;</span>
  96         <span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">range_iterator</span><span class="special">&lt;</span><span class="keyword">const</span> <span class="identifier">R</span><span class="special">&gt;::</span><span class="identifier">type</span> <span class="identifier">is_sorted_until</span> <span class="special">(</span> <span class="keyword">const</span> <span class="identifier">Range</span> <span class="special">&amp;</span><span class="identifier">r</span><span class="special">,</span> <span class="identifier">Pred</span> <span class="identifier">p</span> <span class="special">);</span>
  97
  98         <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Range</span><span class="special">&gt;</span>
  99         <span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">range_iterator</span><span class="special">&lt;</span><span class="keyword">const</span> <span class="identifier">R</span><span class="special">&gt;::</span><span class="identifier">type</span> <span class="identifier">is_sorted_until</span> <span class="special">(</span> <span class="keyword">const</span> <span class="identifier">Range</span> <span class="special">&amp;</span><span class="identifier">r</span> <span class="special">);</span>
 100 <span class="special">}}</span>
 101 </pre>
 102 <p>
 103       </p>
 104 <p>
 105         Iterator requirements: The <code class="computeroutput"><span class="identifier">is_sorted_until</span></code>
 106         functions will work on forward iterators or better. Since they have to return
 107         a place in the input sequence, input iterators will not suffice.
 108       </p>
 109 <p>
 110         Complexity: <code class="computeroutput"><span class="identifier">is_sorted_until</span></code>
 111         will make at most <span class="emphasis"><em>N-1</em></span> calls to the predicate (given
 112         a sequence of length <span class="emphasis"><em>N</em></span>).
 113       </p>
 114 <p>
 115         Examples:
 116       </p>
 117 <p>
 118         Given the sequence <code class="computeroutput"><span class="special">{</span> <span class="number">1</span><span class="special">,</span> <span class="number">2</span><span class="special">,</span>
 119         <span class="number">3</span><span class="special">,</span> <span class="number">4</span><span class="special">,</span> <span class="number">5</span><span class="special">,</span> <span class="number">3</span> <span class="special">}</span></code>,
 120         <code class="computeroutput"><span class="identifier">is_sorted_until</span> <span class="special">(</span>
 121         <span class="identifier">beg</span><span class="special">,</span>
 122         <span class="identifier">end</span><span class="special">,</span>
 123         <span class="identifier">std</span><span class="special">::</span><span class="identifier">less</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;())</span></code>
 124         would return an iterator pointing at the second <code class="computeroutput"><span class="number">3</span></code>.
 125       </p>
 126 <p>
 127         Given the sequence <code class="computeroutput"><span class="special">{</span> <span class="number">1</span><span class="special">,</span> <span class="number">2</span><span class="special">,</span>
 128         <span class="number">3</span><span class="special">,</span> <span class="number">4</span><span class="special">,</span> <span class="number">5</span><span class="special">,</span> <span class="number">9</span> <span class="special">}</span></code>,
 129         <code class="computeroutput"><span class="identifier">is_sorted_until</span> <span class="special">(</span>
 130         <span class="identifier">beg</span><span class="special">,</span>
 131         <span class="identifier">end</span><span class="special">,</span>
 132         <span class="identifier">std</span><span class="special">::</span><span class="identifier">less</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;())</span></code>
 133         would return <code class="computeroutput"><span class="identifier">end</span></code>.
 134       </p>
 135 <p>
 136         There are also a set of "wrapper functions" for is_ordered which
 137         make it easy to see if an entire sequence is ordered. These functions return
 138         a boolean indicating success or failure rather than an iterator to where
 139         the out of order items were found.
 140       </p>
 141 <p>
 142         To test if a sequence is increasing (each element at least as large as the
 143         preceding one):
 144 </p>
 145 <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">algorithm</span> <span class="special">{</span>
 146         <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Iterator</span><span class="special">&gt;</span>
 147         <span class="keyword">bool</span> <span class="identifier">is_increasing</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>
 148
 149         <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">R</span><span class="special">&gt;</span>
 150         <span class="keyword">bool</span> <span class="identifier">is_increasing</span> <span class="special">(</span> <span class="keyword">const</span> <span class="identifier">R</span> <span class="special">&amp;</span><span class="identifier">range</span> <span class="special">);</span>
 151 <span class="special">}}</span>
 152 </pre>
 153 <p>
 154       </p>
 155 <p>
 156         To test if a sequence is decreasing (each element no larger than the preceding
 157         one):
 158       </p>
 159 <p>
 160 </p>
 161 <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">algorithm</span> <span class="special">{</span>
 162         <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">ForwardIterator</span><span class="special">&gt;</span>
 163         <span class="keyword">bool</span> <span class="identifier">is_decreasing</span> <span class="special">(</span> <span class="identifier">ForwardIterator</span> <span class="identifier">first</span><span class="special">,</span> <span class="identifier">ForwardIterator</span> <span class="identifier">last</span> <span class="special">);</span>
 164
 165         <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">R</span><span class="special">&gt;</span>
 166         <span class="keyword">bool</span> <span class="identifier">is_decreasing</span> <span class="special">(</span> <span class="keyword">const</span> <span class="identifier">R</span> <span class="special">&amp;</span><span class="identifier">range</span> <span class="special">);</span>
 167 <span class="special">}}</span>
 168 </pre>
 169 <p>
 170       </p>
 171 <p>
 172         To test if a sequence is strictly increasing (each element larger than the
 173         preceding one):
 174 </p>
 175 <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">algorithm</span> <span class="special">{</span>
 176         <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">ForwardIterator</span><span class="special">&gt;</span>
 177         <span class="keyword">bool</span> <span class="identifier">is_strictly_increasing</span> <span class="special">(</span> <span class="identifier">ForwardIterator</span> <span class="identifier">first</span><span class="special">,</span> <span class="identifier">ForwardIterator</span> <span class="identifier">last</span> <span class="special">);</span>
 178
 179         <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">R</span><span class="special">&gt;</span>
 180         <span class="keyword">bool</span> <span class="identifier">is_strictly_increasing</span> <span class="special">(</span> <span class="keyword">const</span> <span class="identifier">R</span> <span class="special">&amp;</span><span class="identifier">range</span> <span class="special">);</span>
 181 <span class="special">}}</span>
 182 </pre>
 183 <p>
 184       </p>
 185 <p>
 186         To test if a sequence is strictly decreasing (each element smaller than the
 187         preceding one):
 188 </p>
 189 <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">algorithm</span> <span class="special">{</span>
 190         <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">ForwardIterator</span><span class="special">&gt;</span>
 191         <span class="keyword">bool</span> <span class="identifier">is_strictly_decreasing</span> <span class="special">(</span> <span class="identifier">ForwardIterator</span> <span class="identifier">first</span><span class="special">,</span> <span class="identifier">ForwardIterator</span> <span class="identifier">last</span> <span class="special">);</span>
 192
 193         <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">R</span><span class="special">&gt;</span>
 194         <span class="keyword">bool</span> <span class="identifier">is_strictly_decreasing</span> <span class="special">(</span> <span class="keyword">const</span> <span class="identifier">R</span> <span class="special">&amp;</span><span class="identifier">range</span> <span class="special">);</span>
 195 <span class="special">}}</span>
 196 </pre>
 197 <p>
 198       </p>
 199 <p>
 200         Complexity: Each of these calls is just a thin wrapper over <code class="computeroutput"><span class="identifier">is_sorted</span></code>, so they have the same complexity
 201         as <code class="computeroutput"><span class="identifier">is_sorted</span></code>.
 202       </p>
 203 <h5>
 204 <a name="the_boost_algorithm_library.CXX11.is_sorted.h2"></a>
 205         <span class="phrase"><a name="the_boost_algorithm_library.CXX11.is_sorted.notes"></a></span><a class="link" href="is_sorted.html#the_boost_algorithm_library.CXX11.is_sorted.notes">Notes</a>
 206       </h5>
 207 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
 208 <li class="listitem">
 209             The routines <code class="computeroutput"><span class="identifier">is_sorted</span></code>
 210             and <code class="computeroutput"><span class="identifier">is_sorted_until</span></code> are
 211             part of the C++11 standard. When compiled using a C++11 implementation,
 212             the implementation from the standard library will be used.
 213           </li>
 214 <li class="listitem">
 215             <code class="computeroutput"><span class="identifier">is_sorted</span></code> and <code class="computeroutput"><span class="identifier">is_sorted_until</span></code> both return true for
 216             empty ranges and ranges of length one.
 217           </li>
 218 </ul></div>
 219 </div>
 220 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 221 <td align="left"></td>
 222 <td align="right"><div class="copyright-footer">Copyright &#169; 2010-2012 Marshall Clow<p>
 223         Distributed under the Boost Software License, Version 1.0. (See accompanying
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