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| <TITLE>find_first_of()</TITLE> |
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| <H2>find_first_of()</H2> |
| <P><B>Library:</B> <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 <algorithm> |
| |
| namespace std { |
| template <class ForwardIterator1, class ForwardIterator2> |
| ForwardIterator1 find_first_of (ForwardIterator1 start1, |
| ForwardIterator1 finish1, |
| ForwardIterator2 start2, |
| ForwardIterator2 finish2); |
| |
| template <class ForwardIterator1, class ForwardIterator2, |
| class BinaryPredicate> |
| 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 <algorithm> // for find_first_of |
| #include <functional> // for equal_to |
| #include <iostream> // for cout, endl |
| #include <vector> // for vector |
| |
| |
| int main () |
| { |
| // Typedef for convenience. |
| typedef std::vector<int, std::allocator<int> > 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<vector::value_type>()); |
| |
| // Create an output stream iterator. |
| std::ostream_iterator<vector::value_type, char, |
| std::char_traits<char> > out(std::cout, " " ); |
| |
| // Output results. |
| std::cout << "For the vectors { "; |
| std::copy(v1.begin(), v1.end(), out); |
| |
| std:: cout << "} and { "; |
| std::copy(v2.begin(), v2.end(), out); |
| |
| std::cout << "}\nboth versions of find_first_of " |
| << "point to: " << *it1 << 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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