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<div class="titlepage"><div><div><h3 class="title">
<a name="the_boost_algorithm_library.CXX11.is_sorted"></a><a class="link" href="is_sorted.html" title="is_sorted">is_sorted
</a>
</h3></div></div></div>
<p>
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>
contains functions for determining if a sequence is ordered.
</p>
<h5>
<a name="the_boost_algorithm_library.CXX11.is_sorted.h0"></a>
<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>
</h5>
<p>
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>
determines whether or not a sequence is completely sorted according so some
criteria. If no comparison predicate is specified, then std::less_equal is
used (i.e, the test is to see if the sequence is non-decreasing)
</p>
<p>
</p>
<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>
<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>
<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>
<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>
<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="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>
<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>
<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>
<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="special">}}</span>
</pre>
<p>
</p>
<p>
Iterator requirements: The <code class="computeroutput"><span class="identifier">is_sorted</span></code>
functions will work forward iterators or better.
</p>
<h5>
<a name="the_boost_algorithm_library.CXX11.is_sorted.h1"></a>
<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>
</h5>
<p>
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
<code class="computeroutput"><span class="identifier">is_sorted</span> <span class="special">(</span>
<span class="identifier">first</span><span class="special">,</span>
<span class="identifier">last</span> <span class="special">)</span></code>
returns <code class="computeroutput"><span class="identifier">last</span></code>. Otherwise,
it returns the last iterator i in [first,last] for which the range [first,i)
is sorted.
</p>
<p>
In short, it returns the element in the sequence that is "out of order".
If the entire sequence is sorted (according to the predicate), then it will
return <code class="computeroutput"><span class="identifier">last</span></code>.
</p>
<p>
</p>
<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>
<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>
<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>
<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>
<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>
<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>
<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>
<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>
<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="special">}}</span>
</pre>
<p>
</p>
<p>
Iterator requirements: The <code class="computeroutput"><span class="identifier">is_sorted_until</span></code>
functions will work on forward iterators or better. Since they have to return
a place in the input sequence, input iterators will not suffice.
</p>
<p>
Complexity: <code class="computeroutput"><span class="identifier">is_sorted_until</span></code>
will make at most <span class="emphasis"><em>N-1</em></span> calls to the predicate (given
a sequence of length <span class="emphasis"><em>N</em></span>).
</p>
<p>
Examples:
</p>
<p>
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>
<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>,
<code class="computeroutput"><span class="identifier">is_sorted_until</span> <span class="special">(</span>
<span class="identifier">beg</span><span class="special">,</span>
<span class="identifier">end</span><span class="special">,</span>
<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>
would return an iterator pointing at the second <code class="computeroutput"><span class="number">3</span></code>.
</p>
<p>
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>
<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>,
<code class="computeroutput"><span class="identifier">is_sorted_until</span> <span class="special">(</span>
<span class="identifier">beg</span><span class="special">,</span>
<span class="identifier">end</span><span class="special">,</span>
<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>
would return <code class="computeroutput"><span class="identifier">end</span></code>.
</p>
<p>
There are also a set of "wrapper functions" for is_ordered which
make it easy to see if an entire sequence is ordered. These functions return
a boolean indicating success or failure rather than an iterator to where
the out of order items were found.
</p>
<p>
To test if a sequence is increasing (each element at least as large as the
preceding one):
</p>
<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>
<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>
<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>
<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>
<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>
<span class="special">}}</span>
</pre>
<p>
</p>
<p>
To test if a sequence is decreasing (each element no larger than the preceding
one):
</p>
<p>
</p>
<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>
<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>
<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>
<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>
<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>
<span class="special">}}</span>
</pre>
<p>
</p>
<p>
To test if a sequence is strictly increasing (each element larger than the
preceding one):
</p>
<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>
<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>
<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>
<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>
<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>
<span class="special">}}</span>
</pre>
<p>
</p>
<p>
To test if a sequence is strictly decreasing (each element smaller than the
preceding one):
</p>
<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>
<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>
<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>
<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>
<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>
<span class="special">}}</span>
</pre>
<p>
</p>
<p>
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
as <code class="computeroutput"><span class="identifier">is_sorted</span></code>.
</p>
<h5>
<a name="the_boost_algorithm_library.CXX11.is_sorted.h2"></a>
<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>
</h5>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
The routines <code class="computeroutput"><span class="identifier">is_sorted</span></code>
and <code class="computeroutput"><span class="identifier">is_sorted_until</span></code> are
part of the C++11 standard. When compiled using a C++11 implementation,
the implementation from the standard library will be used.
</li>
<li class="listitem">
<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
empty ranges and ranges of length one.
</li>
</ul></div>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright &#169; 2010-2012 Marshall Clow<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
</p>
</div></td>
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