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135 lines
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<HTML>
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<HEAD>
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<TITLE>lexicographical_compare()</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="less-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="limits-h.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>lexicographical_compare()</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">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 returns <SAMP>true</SAMP> if one sequence compares lexicographically less than another, <SAMP>false</SAMP> otherwise</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 InputIterator1, class InputIterator2>
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bool
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lexicographical_compare(InputIterator1 start1,
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InputIterator1 finish1,
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InputIterator2 start2,
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InputIterator2 finish2);
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template <class InputIterator1, class InputIterator2,
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class Compare>
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bool
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lexicographical_compare(InputIterator1 start1,
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InputIterator1 finish1,
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InputIterator2 start2,
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InputIterator2 finish2,
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Compare comp);
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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>lexicographical_compare()</SAMP> functions compare each element in the range <SAMP>[start1, finish1)</SAMP> to the corresponding element in the range <SAMP>[start2, finish2)</SAMP> using iterators <SAMP>i</SAMP> and <SAMP>j</SAMP>. </P>
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<P>The first version of the algorithm uses <SAMP>operator<()</SAMP> as the default comparison operator. It immediately returns <SAMP>true</SAMP> if it encounters any pair in which <SAMP>*i</SAMP> is less than <SAMP>*j</SAMP>, and immediately returns <SAMP>false</SAMP> if <SAMP>*j</SAMP> is less than <SAMP>*i</SAMP>. If the algorithm reaches the end of the first sequence before reaching the end of the second sequence, it also returns <SAMP>true</SAMP>. </P>
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<P>The second version of the function takes an argument <SAMP>comp</SAMP> that defines a comparison function that is used in place of the default <SAMP>operator<()</SAMP>.</P>
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<P>The <SAMP>lexicographical_compare()</SAMP> functions can be used with all the data types included in the standard library.</P>
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<A NAME="sec5"><H3>Complexity</H3></A>
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<P><SAMP>lexicographical_compare()</SAMP> performs at most <SAMP>min((finish1 - start1), (finish2 - start2))</SAMP> applications of the comparison function.</P>
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<A NAME="sec6"><H3>Example</H3></A>
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<UL><PRE>//
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// lex_comp.cpp
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//
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#include <algorithm>
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#include <functional>
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#include <iostream>
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#include <vector>
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int main()
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{
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typedef std::vector<int, std::allocator<int> > Vector;
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const Vector::value_type d1[] = { 1, 3, 5, 32, 64 };
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const Vector::value_type d2[] = { 1, 3, 2, 43, 56 };
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// Create vectors.
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Vector v1 (d1 + 0, d1 + sizeof d1 / sizeof *d1);
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Vector v2 (d2 + 0, d2 + sizeof d1 / sizeof *d2);
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// Is v1 less than v2 (I think not).
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bool b1 = std::lexicographical_compare (v1.begin (),
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v1.end (), v2.begin (), v2.end ());
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// Is v2 less than v1 (yup, sure is).
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bool b2 = std::lexicographical_compare(v2.begin (),
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v2.end (), v1.begin (), v1.end (),
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std::less<int>());
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std::cout << std::boolalpha << b1
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<< " " << b2 << std::endl;
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return 0;
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}
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Program Output:
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</PRE></UL>
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<UL><PRE>false true
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</PRE></UL>
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<A NAME="sec7"><H3>Standards Conformance</H3></A>
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<P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 25.3.8</I></P>
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<BR>
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