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It is provided "as is" without express or implied warranty. -- --><Head><Title>remove_if</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>remove_if</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 remove_if(ForwardIterator first, ForwardIterator last, Predicate pred);</pre> <h3>Description</h3><tt>Remove_if</tt> removes from the range <tt>[first, last)</tt> every element <tt>x</tt> suchthat <tt>pred(x)</tt> is <tt>true</tt>. That is, <tt>remove_if</tt>returns an iterator <tt>new_last</tt> such that the range <tt>[first, new_last)</tt>contains no elements for which <tt>pred</tt> is <tt>true</tt>. <A href="#1">[1]</A> The iterators inthe range <tt>[new_last, last)</tt> are all still dereferenceable, but theelements that they point to are unspecified. <tt>Remove_if</tt> is stable,meaning that the relative order of elements that are not removed isunchanged.<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>ForwardIterator</tt> is mutable.<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. <tt>Remove_if</tt> performs exactly <tt>last - first</tt> applicationsof <tt>pred</tt>.<h3>Example</h3>Remove all even numbers from a vector.<pre><A href="Vector.html">vector</A><int> V;V.push_back(1);V.push_back(4);V.push_back(2);V.push_back(8);V.push_back(5);V.push_back(7);<A href="copy.html">copy</A>(V.begin(), V.end(), <A href="ostream_iterator.html">ostream_iterator</A><int>(cout, " ")); // The output is "1 4 2 8 5 7"<A href="Vector.html">vector</A><int>::iterator new_end = remove_if(V.begin(), V.end(), <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)));V.erase(new_end, V.end()); <A href="#1">[1]</A><A href="copy.html">copy</A>(V.begin(), V.end(), <A href="ostream_iterator.html">ostream_iterator</A><int>(cout, " ")); // The output is "1 5 7".</pre><h3>Notes</h3><P><A name="1">[1]</A>The meaning of "removal" is somewhat subtle. <tt>Remove_if</tt>does not destroy any iterators, and does not change the distancebetween <tt>first</tt> and <tt>last</tt>. (There's no way that it could do anythingof the sort.) So, for example, if <tt>V</tt> is a <A href="Vector.html">vector</A>,<tt>remove_if(V.begin(), V.end(), pred)</tt> does not change <tt>V.size()</tt>: <tt>V</tt> willcontain just as many elements as it did before. <tt>Remove_if</tt> returns aniterator that points to the end of the resulting range after elementshave been removed from it; it follows that the elements after thatiterator are of no interest, and may be discarded. If you areremoving elements from a <A href="Sequence.html">Sequence</A>, you may simply erase them.That is, a reasonable way of removing elements from a <A href="Sequence.html">Sequence</A>is <tt>S.erase(remove_if(S.begin(), S.end(), pred), S.end())</tt>.<h3>See also</h3><tt><A href="remove.html">remove</A></tt>, <tt><A href="remove_copy.html">remove_copy</A></tt>, <tt><A href="remove_copy_if.html">remove_copy_if</A></tt>,<tt><A href="unique.html">unique</A></tt>, <tt><A href="unique_copy.html">unique_copy</A></tt>.<!-- 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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