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<H2>find_first_of()</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 the first occurrence of any value from one sequence in another sequence</P>
<A NAME="sec3"><H3>Synopsis</H3></A>

<PRE>#include &lt;algorithm&gt;

namespace std {
  template &lt;class ForwardIterator1, class ForwardIterator2&gt;
  ForwardIterator1 find_first_of (ForwardIterator1 start1,
                                  ForwardIterator1 finish1,
                                  ForwardIterator2 start2,
                                  ForwardIterator2 finish2);

  template &lt;class ForwardIterator1, class ForwardIterator2,
            class BinaryPredicate&gt;
  ForwardIterator1 find_first_of (ForwardIterator1 start1,
                                  ForwardIterator1 finish1,
                                  ForwardIterator2 start2,
                                  ForwardIterator2 finish2,
                                  BinaryPredicate binary_pred);
}
</PRE>
<A NAME="sec4"><H3>Description</H3></A>
<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>
<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>

<UL><PRE>*i == *j, binary_pred(*i,*j) == true.
</PRE></UL>
<P>Or <SAMP>find_first_of()</SAMP> returns <SAMP>finish1</SAMP> if no such iterator is found.</P>
<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>
<A NAME="sec5"><H3>Complexity</H3></A>
<P>At most <SAMP>(finish1 - start1)*(finish2 - start2)</SAMP> applications of the corresponding predicate are done.</P>
<A NAME="sec6"><H3>Example</H3></A>

<UL><PRE>//
// find_f_o.cpp
//

#include &lt;algorithm&gt;    // for find_first_of
#include &lt;functional&gt;   // for equal_to
#include &lt;iostream&gt;     // for cout, endl
#include &lt;vector&gt;       // for vector


int main ()
{
    // Typedef for convenience.
    typedef std::vector&lt;int, std::allocator&lt;int&gt; &gt; vector;

    const vector::value_type a1[] = { 
        0, 1, 2, 2, 3, 4, 2, 2, 6, 7 
    };
    const vector::value_type a2[] = { 6, 4 };

    // Set up two vectors.
    const vector v1(a1, a1 + sizeof a1 / sizeof *a1);
    const vector v2(a2, a2 + sizeof a2 / sizeof *a2);

    // Try both find_first_of variants.
    vector::const_iterator it1 =
        std::find_first_of(v1.begin(), v1.end(), 
                           v2.begin(), v2.end()); 

    vector::const_iterator it2 =
        std::find_first_of(v1.begin(), v1.end(), 
                           v2.begin(), v2.end(),
                        std::equal_to&lt;vector::value_type&gt;());

    // Create an output stream iterator.
    std::ostream_iterator&lt;vector::value_type, char,
        std::char_traits&lt;char&gt; &gt; out(std::cout, " " );

    // Output results.
    std::cout &lt;&lt; "For the vectors { ";
    std::copy(v1.begin(), v1.end(), out);

    std:: cout &lt;&lt; "} and { ";
    std::copy(v2.begin(), v2.end(), out);

    std::cout &lt;&lt; "}\nboth versions of find_first_of "
              &lt;&lt; "point to: " &lt;&lt; *it1 &lt;&lt; std::endl; 

    // Return 0 on success, non-0 on failure.
    return !(*it1 == *it2);
}


Program Output
</PRE></UL>
<UL><PRE>For the vectors { 0 1 2 2 3 4 2 2 6 7 } and { 6 4 }
both versions of find_first_of point to: 4
</PRE></UL>
<A NAME="sec7"><H3>See Also</H3></A>
<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>
<A NAME="sec8"><H3>Standards Conformance</H3></A>
<P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 25.1.4</I></P>

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