blob: b6dfd698af332b15b75d0437434c08e30f8af85a [file] [log] [blame]
<!--
Licensed to the Apache Software Foundation (ASF) under one or more
contributor license agreements. See the NOTICE file distributed
with this work for additional information regarding copyright
ownership. The ASF licenses this file to you under the Apache
License, Version 2.0 (the License); you may not use this file
except in compliance with the License. You may obtain a copy of
the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
implied. See the License for the specific language governing
permissions and limitations under the License.
Copyright 1999-2007 Rogue Wave Software, Inc.
-->
<HTML>
<HEAD>
<TITLE>find_if()</TITLE>
<LINK REL=StyleSheet HREF="../rw.css" TYPE="text/css" TITLE="Apache stdcxx Stylesheet"></HEAD>
<BODY BGCOLOR=#FFFFFF>
<A HREF="find-first-of.html"><IMG SRC="images/bprev.gif" WIDTH=20 HEIGHT=21 ALT="Previous file" BORDER=O></A><A HREF="noframes.html"><IMG SRC="images/btop.gif" WIDTH=56 HEIGHT=21 ALT="Top of Document" BORDER=O></A><A HREF="booktoc.html"><IMG SRC="images/btoc.gif" WIDTH=56 HEIGHT=21 ALT="Contents" BORDER=O></A><A HREF="tindex.html"><IMG SRC="images/bindex.gif" WIDTH=56 HEIGHT=21 ALT="Index page" BORDER=O></A><A HREF="for-each.html"><IMG SRC="images/bnext.gif" WIDTH=25 HEIGHT=21 ALT="Next file" BORDER=O></A><DIV CLASS="DOCUMENTNAME"><B>Apache C++ Standard Library Reference Guide</B></DIV>
<H2>find_if()</H2>
<P><B>Library:</B>&nbsp;&nbsp;<A HREF="2-9.html">Algorithms</A></P>
<PRE><HR><B><I>Function</I></B><HR></PRE>
<UL>
<LI><A HREF="#sec1">Local Index</A></LI>
<LI><A HREF="#sec2">Summary</A></LI>
<LI><A HREF="#sec3">Synopsis</A></LI>
<LI><A HREF="#sec4">Description</A></LI>
<LI><A HREF="#sec5">Complexity</A></LI>
<LI><A HREF="#sec6">Example</A></LI>
<LI><A HREF="#sec7">See Also</A></LI>
<LI><A HREF="#sec8">Standards Conformance</A></LI>
</UL>
<A NAME="sec1"><H3>Local Index</H3></A>
No Entries
<A NAME="sec2"><H3>Summary</H3></A>
<P>Algorithm that finds an occurrence of a value in a sequence that satisfies a specified predicate</P>
<A NAME="sec3"><H3>Synopsis</H3></A>
<PRE>#include &lt;algorithm&gt;
namespace std {
template &lt;class InputIterator, class Predicate&gt;
InputIterator find_if(InputIterator start,
InputIterator finish,
Predicate pred);
}
</PRE>
<A NAME="sec4"><H3>Description</H3></A>
<P>The <SAMP>find_if()</SAMP> algorithm allows you to search for the first element in a sequence that satisfies a particular condition. The sequence is defined by iterators <SAMP>start</SAMP> and <SAMP>finish</SAMP>, while the condition is defined by the third argument: a predicate function that returns a boolean value. <SAMP>find_if()</SAMP> returns the first iterator <SAMP>i</SAMP> in the range <SAMP>[start, finish)</SAMP> for which the following condition holds:</P>
<P><SAMP>pred(*i) == true.</SAMP></P>
<P>If no such iterator is found, <SAMP>find_if()</SAMP> returns <SAMP>finish</SAMP>.</P>
<A NAME="sec5"><H3>Complexity</H3></A>
<P><SAMP>find_if()</SAMP> performs at most <SAMP>finish-start</SAMP> applications of the corresponding predicate.</P>
<A NAME="sec6"><H3>Example</H3></A>
<UL><PRE>//
// find.cpp
//
#include &lt;vector&gt; // for vector
#include &lt;algorithm&gt; // for adjacent_find, find
#include &lt;functional&gt; // for bind1st, equal_to
#include &lt;iostream&gt; // for cout, endl
int main ()
{
// Typedef for convenience.
typedef std::vector&lt;int, std::allocator&lt;int&gt; &gt; Vector;
const Vector::value_type arr[] = { 0, 1, 2, 2, 3,
4, 2, 2, 6, 7 };
// Set up a vector.
const Vector v1 (arr, arr + sizeof arr / sizeof *arr);
// Try find.
Vector::const_iterator it = std::find (v1.begin (),
v1.end (), 3);
std::cout &lt;&lt; *it &lt;&lt; ' ';
// Try find_if.
it = std::find_if (v1.begin (), v1.end (),
std::bind1st (std::equal_to&lt;Vector::value_type&gt;(),
3));
std::cout &lt;&lt; *it &lt;&lt; ' ';
// Try both adjacent_find variants.
it = std::adjacent_find (v1.begin (), v1.end ());
std::cout &lt;&lt; *it &lt;&lt; ' ';
it = std::adjacent_find (v1.begin (), v1.end (),
std::equal_to&lt;Vector::value_type&gt;());
std::cout &lt;&lt; *it &lt;&lt; std::endl;
return 0;
}
Program Output:
</PRE></UL>
<UL><PRE>3 3 2 2
</PRE></UL>
<A NAME="sec7"><H3>See Also</H3></A>
<P><SAMP><A HREF="adjacent-find.html">adjacent_find()</A></SAMP>, <A HREF="algorithms.html">Algorithms</A>, <SAMP><A HREF="find.html">find()</A></SAMP>, <SAMP><A HREF="find-end.html">find_end()</A></SAMP>, <SAMP><A HREF="find-first-of.html">find_first_of()</A></SAMP></P>
<A NAME="sec8"><H3>Standards Conformance</H3></A>
<P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 25.1.2</I></P>
<BR>
<HR>
<A HREF="find-first-of.html"><IMG SRC="images/bprev.gif" WIDTH=20 HEIGHT=21 ALT="Previous file" BORDER=O></A><A HREF="noframes.html"><IMG SRC="images/btop.gif" WIDTH=56 HEIGHT=21 ALT="Top of Document" BORDER=O></A><A HREF="booktoc.html"><IMG SRC="images/btoc.gif" WIDTH=56 HEIGHT=21 ALT="Contents" BORDER=O></A><A HREF="tindex.html"><IMG SRC="images/bindex.gif" WIDTH=56 HEIGHT=21 ALT="Index page" BORDER=O></A><A HREF="for-each.html"><IMG SRC="images/bnext.gif" WIDTH=20 HEIGHT=21 ALT="Next file" BORDER=O></A>
<!-- Google Analytics tracking code -->
<script src="http://www.google-analytics.com/urchin.js" type="text/javascript">
</script>
<script type="text/javascript">
_uacct = "UA-1775151-1";
urchinTracker();
</script>
<!-- end of Google Analytics tracking code -->
</BODY>
</HTML>