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| <TITLE>equal_range()</TITLE> |
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| <A HREF="equal.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="equal-to.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>equal_range()</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 largest subrange in a range of values into which a given value can be inserted without violating the ordering of the values</P> |
| <A NAME="sec3"><H3>Synopsis</H3></A> |
| |
| <PRE>#include <algorithm> |
| |
| namespace std { |
| template <class ForwardIterator, class T> |
| pair<ForwardIterator, ForwardIterator> |
| equal_range(ForwardIterator start, ForwardIterator finish, |
| const T& value); |
| |
| template <class ForwardIterator, class T, class Compare> |
| pair<ForwardIterator, ForwardIterator> |
| equal_range(ForwardIterator start, ForwardIterator finish, |
| const T& value, Compare comp); |
| } |
| </PRE> |
| <A NAME="sec4"><H3>Description</H3></A> |
| <P>The <SAMP>equal_range()</SAMP> algorithm performs a binary search on an ordered range to determine where the element <SAMP>value</SAMP> can be inserted without violating the range's ordering. The library includes two versions of the algorithm. The first version uses <SAMP>operator<()</SAMP> to search for the valid insertion range, and assumes that the sequence was sorted using the same ordering. The second version allows you to specify a function object of type <SAMP>Compare</SAMP>, and assumes that <SAMP>Compare</SAMP> was the function used to sort the sequence. The function object must be a binary predicate. </P> |
| <P><SAMP>equal_range()</SAMP> returns a pair of iterators, <SAMP>i</SAMP> and <SAMP>j</SAMP>, that define a range containing elements equivalent to <SAMP>value</SAMP>, in other words, the first and last valid insertion points for <SAMP>value</SAMP>. If <SAMP>value</SAMP> is not an element in the container, <SAMP>i</SAMP> and <SAMP>j</SAMP> are equal. Otherwise, <SAMP>i</SAMP> points to the first element not "less" than <SAMP>value</SAMP>, and <SAMP>j</SAMP> points to the first element greater than value. In the second version, the ordering is defined by the comparison object. Formally, <SAMP>equal_range()</SAMP> returns a sub-range <SAMP>[i, j)</SAMP> such that <SAMP>value</SAMP> can be inserted at any iterator <SAMP>k</SAMP> within the range without violating the ordering. Depending upon the version of the algorithm used, <SAMP>k</SAMP> must satisfy one of the following conditions: </P> |
| <P><SAMP>!(*k < value) && !(value < *k)</SAMP></P> |
| <P> or </P> |
| <P><SAMP>comp(*k,value) == false && comp(value, *k) == false</SAMP></P> |
| <P>The range <SAMP>[start,finish)</SAMP> is assumed to be sorted. Type <SAMP>T</SAMP> must be LessThanComparable.</P> |
| <A NAME="sec5"><H3>Complexity</H3></A> |
| <P><SAMP>equal_range()</SAMP> performs at most <SAMP>2 * log(finish - start) + 1</SAMP> comparisons.</P> |
| <A NAME="sec6"><H3>Example</H3></A> |
| |
| <UL><PRE>// |
| // eqlrange.cpp |
| // |
| |
| #include <algorithm> |
| #include <functional> |
| #include <iostream> |
| #include <vector> |
| |
| |
| |
| int main () |
| { |
| // Typedef for convenience. |
| typedef std::vector<int, std::allocator<int> > vector; |
| |
| vector::value_type arr[] = { |
| 0, 1, 2, 2, 3, 4, 2, 2, 2, 6, 7 |
| }; |
| |
| // Set up a vector. |
| vector v1 (arr, arr + sizeof arr / sizeof *arr); |
| |
| // Try equal_range variants. |
| std::pair<vector::iterator, vector::iterator> p1 = |
| std::equal_range (v1.begin (), v1.end (), 3); |
| |
| std::pair<vector::iterator, vector::iterator> p2 = |
| std::equal_range (v1.begin (), v1.end (), 2, |
| std::less<vector::value_type> ()); |
| |
| // Output results. |
| std::cout << "\nThe equal range for 3 is: " |
| << "(" << *p1.first << " , " |
| << *p1.second << ")" << std::endl; |
| |
| std::cout << "\nThe equal range for 2 is: " |
| << "(" << *p2.first << " , " |
| << *p2.second << ")" << std::endl; |
| |
| return 0; |
| } |
| |
| |
| Program Output |
| </PRE></UL> |
| <UL><PRE> |
| The equal range for 3 is: (3 , 4) |
| |
| The equal range for 2 is: (2 , 3) |
| </PRE></UL> |
| <A NAME="sec7"><H3>See Also</H3></A> |
| <P><B><I><A HREF="binary-function.html">binary_function</A></I></B>, <SAMP><A HREF="lower-bound.html">lower_bound()</A></SAMP>, <SAMP><A HREF="upper-bound.html">upper_bound()</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 25.3.3.3</I></P> |
| |
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