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It is provided "as is" without express or implied warranty. -- --><Head><Title>partition</Title><!-- Generated by htmldoc --></HEAD><BODY TEXT="#000000" LINK="#006600" ALINK="#003300" VLINK="#7C7F87" BGCOLOR="#FFFFFF"><A HREF="/"><IMG SRC="/images/common/sgilogo_small.gif" ALT="SGI Logo" WIDTH="80" HEIGHT="72" BORDER="0"></A><P><!--end header--><BR Clear><H1>partition</H1><Table CellPadding=0 CellSpacing=0 width=100%><TR><TD Align=left><Img src = "algorithms.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD><TD Align=right><Img src = "function.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD></TR><TR><TD Align=left VAlign=top><b>Category</b>: algorithms</TD><TD Align=right VAlign=top><b>Component type</b>: function</TD></TR></Table><h3>Prototype</h3><pre>template <class <A href="ForwardIterator.html">ForwardIterator</A>, class <A href="Predicate.html">Predicate</A>>ForwardIterator partition(ForwardIterator first, ForwardIterator last, Predicate pred) </pre> <h3>Description</h3><tt>Partition</tt> reorders the elements in the range <tt>[first, last)</tt> basedon the <A href="functors.html">function object</A> <tt>pred</tt>, such thatthe elements that satisfy <tt>pred</tt> precede the elementsthat fail to satisfy it. The postcondition is that, for someiterator <tt>middle</tt> in the range <tt>[first, last)</tt>, <tt>pred(*i)</tt> is <tt>true</tt> for every iterator <tt>i</tt> in the range <tt>[first, middle)</tt> and<tt>false</tt> for every iterator <tt>i</tt> in the range <tt>[middle, last)</tt>. <A href="#1">[1]</A> The return value of <tt>partition</tt> is <tt>middle</tt>.<h3>Definition</h3>Defined in the standard header <A href="algorithm">algorithm</A>, and in the nonstandardbackward-compatibility header <A href="algo.h">algo.h</A>.<h3>Requirements on types</h3><UL><LI><tt>ForwardIterator</tt> is a model of <A href="ForwardIterator.html">Forward Iterator</A>.<LI><tt>Predicate</tt> is a model of <A href="Predicate.html">Predicate</A>.<LI><tt>ForwardIterator</tt>'s value type is convertible to <tt>Predicate</tt>'s argument type.</UL><h3>Preconditions</h3><UL><LI><tt>[first, last)</tt> is a valid range.</UL><h3>Complexity</h3>Linear. Exactly <tt>last - first</tt> applications of <tt>pred</tt>, and at most<tt>(last - first)/2</tt> swaps.<h3>Example</h3>Reorder a sequence so that even numbers precede odd numbers.<pre>int A[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};const int N = sizeof(A)/sizeof(int);partition(A, A + N, <A href="unary_compose.html">compose1</A>(<A href="binder2nd.html">bind2nd</A>(<A href="equal_to.html">equal_to</A><int>(), 0), <A href="binder2nd.html">bind2nd</A>(<A href="modulus.html">modulus</A><int>(), 2)));<A href="copy.html">copy</A>(A, A + N, <A href="ostream_iterator.html">ostream_iterator</A><int>(cout, " "));// The output is "10 2 8 4 6 5 7 3 9 1". <A href="#1">[1]</A></pre><h3>Notes</h3><P><A name="1">[1]</A>The relative order of elements in these two blocks is not necessarilythe same as it was in the original sequence. A different algorithm, <tt><A href="stable_partition.html">stable_partition</A></tt>, does guarantee to preserve the relative order.<h3>See also</h3><tt><A href="stable_partition.html">stable_partition</A></tt>, <A href="Predicate.html">Predicate</A>, <A href="functors.html">function object</A> <!-- start footer --><!-- Footer Begins --><STYLE TYPE="text/css"><!--TD.footer, TD.footer A{ font-family: Arial, helvetica, sans-serif; font-size: 8pt;}A.home {font-family: Arial, helvetica, sans-serif;}--></STYLE><P><A CLASS="home" HREF="index.html">STL Home</A><P><TABLE WIDTH="600" CELLPADDING="0" CELLPADDING="0" BORDER="0"> <TR> <TD ALIGN="RIGHT" CLASS="footer"><A HREF="/company_info/terms.html" TARGET="_top">terms of use</A> | <A HREF="/company_info/privacy.html" TARGET="_top">privacy policy</A></TD> <TD ALIGN="CENTER" CLASS="footer"> | </TD> <TD ALIGN="LEFT" CLASS="footer"><A HREF="/cgi-bin/feedback/" TARGET="_top">contact us</A></TD> </TR><TR> <TD ALIGN="RIGHT" CLASS="footer">Copyright © 1993-2003 Silicon Graphics, Inc. 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