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156 lines
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<HEAD>
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<TITLE>find_first_of()</TITLE>
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<LINK REL=StyleSheet HREF="../rw.css" TYPE="text/css" TITLE="Apache stdcxx Stylesheet"></HEAD>
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<A HREF="find-end.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="find-if.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>
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<H2>find_first_of()</H2>
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<P><B>Library:</B> <A HREF="2-9.html">Algorithms</A></P>
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<PRE><HR><B><I>Function</I></B><HR></PRE>
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<UL>
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<LI><A HREF="#sec1">Local Index</A></LI>
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<LI><A HREF="#sec2">Summary</A></LI>
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<LI><A HREF="#sec3">Synopsis</A></LI>
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<LI><A HREF="#sec4">Description</A></LI>
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<LI><A HREF="#sec5">Complexity</A></LI>
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<LI><A HREF="#sec6">Example</A></LI>
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<LI><A HREF="#sec7">See Also</A></LI>
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<LI><A HREF="#sec8">Standards Conformance</A></LI>
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</UL>
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<A NAME="sec1"><H3>Local Index</H3></A>
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No Entries
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<A NAME="sec2"><H3>Summary</H3></A>
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<P>Algorithm that finds the first occurrence of any value from one sequence in another sequence</P>
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<A NAME="sec3"><H3>Synopsis</H3></A>
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<PRE>#include <algorithm>
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namespace std {
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template <class ForwardIterator1, class ForwardIterator2>
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ForwardIterator1 find_first_of (ForwardIterator1 start1,
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ForwardIterator1 finish1,
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ForwardIterator2 start2,
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ForwardIterator2 finish2);
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template <class ForwardIterator1, class ForwardIterator2,
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class BinaryPredicate>
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ForwardIterator1 find_first_of (ForwardIterator1 start1,
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ForwardIterator1 finish1,
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ForwardIterator2 start2,
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ForwardIterator2 finish2,
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BinaryPredicate binary_pred);
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}
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</PRE>
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<A NAME="sec4"><H3>Description</H3></A>
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<P>The <SAMP>find_first_of()</SAMP> algorithm finds the first occurrence of a value from a sequence, specified by <SAMP>start2, finish2</SAMP>, in a sequence specified by <SAMP>start1, finish1</SAMP>. The algorithm returns an iterator in the range <SAMP>[start1, finish1) </SAMP>that points to the first matching element<SAMP>.</SAMP> If the first sequence <SAMP>[start1, finish1)</SAMP> does not contain any of the values in the second sequence, <SAMP>find_first_of()</SAMP> returns <SAMP>finish1</SAMP>. </P>
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<P>In other words, <SAMP>find_first_of()</SAMP> returns the first iterator <SAMP>i</SAMP> in <SAMP>[start1, finish1)</SAMP>such that for some iterator <SAMP>j</SAMP> in the range <SAMP>[start2, finish2)</SAMP>, the following conditions hold: </P>
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<UL><PRE>*i == *j, binary_pred(*i,*j) == true.
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</PRE></UL>
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<P>Or <SAMP>find_first_of()</SAMP> returns <SAMP>finish1</SAMP> if no such iterator is found.</P>
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<P>Two versions of the algorithm exist. The first uses the equality operator as the default binary predicate, and the second allows you to specify a binary predicate.</P>
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<A NAME="sec5"><H3>Complexity</H3></A>
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<P>At most <SAMP>(finish1 - start1)*(finish2 - start2)</SAMP> applications of the corresponding predicate are done.</P>
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<A NAME="sec6"><H3>Example</H3></A>
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<UL><PRE>//
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// find_f_o.cpp
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//
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#include <algorithm> // for find_first_of
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#include <functional> // for equal_to
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#include <iostream> // for cout, endl
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#include <vector> // for vector
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int main ()
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{
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// Typedef for convenience.
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typedef std::vector<int, std::allocator<int> > vector;
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const vector::value_type a1[] = {
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0, 1, 2, 2, 3, 4, 2, 2, 6, 7
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};
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const vector::value_type a2[] = { 6, 4 };
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// Set up two vectors.
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const vector v1(a1, a1 + sizeof a1 / sizeof *a1);
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const vector v2(a2, a2 + sizeof a2 / sizeof *a2);
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// Try both find_first_of variants.
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vector::const_iterator it1 =
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std::find_first_of(v1.begin(), v1.end(),
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v2.begin(), v2.end());
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vector::const_iterator it2 =
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std::find_first_of(v1.begin(), v1.end(),
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v2.begin(), v2.end(),
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std::equal_to<vector::value_type>());
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// Create an output stream iterator.
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std::ostream_iterator<vector::value_type, char,
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std::char_traits<char> > out(std::cout, " " );
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// Output results.
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std::cout << "For the vectors { ";
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std::copy(v1.begin(), v1.end(), out);
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std:: cout << "} and { ";
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std::copy(v2.begin(), v2.end(), out);
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std::cout << "}\nboth versions of find_first_of "
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<< "point to: " << *it1 << std::endl;
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// Return 0 on success, non-0 on failure.
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return !(*it1 == *it2);
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}
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Program Output
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</PRE></UL>
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<UL><PRE>For the vectors { 0 1 2 2 3 4 2 2 6 7 } and { 6 4 }
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both versions of find_first_of point to: 4
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</PRE></UL>
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<A NAME="sec7"><H3>See Also</H3></A>
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<P><A HREF="algorithms.html">Algorithms</A>, <SAMP><A HREF="adjacent-find.html">adjacent_find()</A></SAMP>, <SAMP><A HREF="find.html">find()</A></SAMP>, <SAMP><A HREF="find-if.html">find_if()</A></SAMP>, <SAMP><A HREF="find-end.html">find_end()</A></SAMP></P>
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<A NAME="sec8"><H3>Standards Conformance</H3></A>
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<P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 25.1.4</I></P>
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