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It is provided "as is" without express or implied warranty. -- --><Head><Title>lexicographical_compare_3way</Title><!-- Generated by htmldoc --></HEAD><BODY TEXT="#000000" LINK="#006600" ALINK="#003300" VLINK="#7C7F87" BGCOLOR="#FFFFFF"><A HREF="/"><IMG SRC="/images/common/sgilogo_small.gif" ALT="SGI Logo" WIDTH="80" HEIGHT="72" BORDER="0"></A><P><!--end header--><BR Clear><H1>lexicographical_compare_3way</H1><Table CellPadding=0 CellSpacing=0 width=100%><TR><TD Align=left><Img src = "algorithms.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD><TD Align=right><Img src = "function.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD></TR><TR><TD Align=left VAlign=top><b>Category</b>: algorithms</TD><TD Align=right VAlign=top><b>Component type</b>: function</TD></TR></Table><h3>Prototype</h3><pre>template <class <A href="InputIterator.html">InputIterator</A>1, class <A href="InputIterator.html">InputIterator</A>2>int lexicographical_compare_3way(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2);</pre> <h3>Description</h3><tt>Lexicographical_compare_3way</tt> is essentially a generalization of thefunction <tt>strcmp</tt> from the standard C library: it returns a negativenumber if the range <tt>[first1, last1)</tt> is lexicographically less thanthe range <tt>[first2, last2)</tt>, a positive number if <tt>[first2, last2)</tt> islexicographically less than <tt>[first1, last1)</tt>, and zero if neitherrange is lexicographically less than the other. <A href="#1">[1]</A><P>As with <tt><A href="lexicographical_compare.html">lexicographical_compare</A></tt>, lexicographical comparisonmeans "dictionary" (element-by-element) ordering. That is,<tt>lexicographical_compare_3way</tt> returns a negative number if<tt>*first1</tt> is less than <tt>*first2</tt>, and a positive number if <tt>*first1</tt>is greater than <tt>*first2</tt>. If the two first elements are equivalent <A href="#2">[2]</A>then <tt>lexicographical_compare_3way</tt> compares the two second elements,and so on. <tt>Lexicographical_compare_3way</tt> returns <tt>0</tt> only if the two ranges<tt>[first1, last1)</tt> and <tt>[first2, last2)</tt> have the same length and ifevery element in the first range is equivalent to its correspondingelement in the second.<h3>Definition</h3>Defined in the standard header <A href="algorithm">algorithm</A>, and in the nonstandardbackward-compatibility header <A href="algo.h">algo.h</A>. This function is an SGIextension; it is not part of the C++ standard.<h3>Requirements on types</h3><UL><LI><tt>InputIterator1</tt> is a model of <A href="InputIterator.html">Input Iterator</A>.<LI><tt>InputIterator2</tt> is a model of <A href="InputIterator.html">Input Iterator</A>.<LI><tt>InputIterator1</tt>'s value type is a model of <A href="LessThanComparable.html">LessThan Comparable</A>.<LI><tt>InputIterator2</tt>'s value type is a model of <A href="LessThanComparable.html">LessThan Comparable</A>.<LI>If <tt>v1</tt> is an object of <tt>InputIterator1</tt>'s value type and <tt>v2</tt> is an object of <tt>InputIterator2</tt>'s value type, then both <tt>v1 < v2</tt> and <tt>v2 < v1</tt> are defined.<LI><tt>Operator<</tt> is a <i>strict weak ordering</i>, as defined in the <A href="LessThanComparable.html">LessThan Comparable</A> requirements.</UL><h3>Preconditions</h3><UL><LI><tt>[first1, last1)</tt> is a valid range.<LI><tt>[first2, last2)</tt> is a valid range.</UL><h3>Complexity</h3>Linear. At most <tt>2 * min(last1 - first1, last2 - first2)</tt> comparisons.<h3>Example</h3><pre>int main(){ int A1[] = {3, 1, 4, 2, 8, 5, 7}; int A2[] = {3, 1, 4, 1, 5, 9, 3}; int A3[] = {1, 2, 3, 4}; int A4[] = {1, 2, 3, 4, 5}; const int N1 = sizeof(A1) / sizeof(int); const int N2 = sizeof(A2) / sizeof(int); const int N3 = sizeof(A3) / sizeof(int); const int N4 = sizeof(A4) / sizeof(int); int C12 = lexicographical_compare_3way(A1, A1 + N1, A2, A2 + N2); int C34 = lexicographical_compare_3way(A3, A3 + N3, A4, A4 + N4); cout << "A1[] and A2[]: " << C12 << endl; cout << "A3[] and A4[]: " << C34 << endl;}</pre><h3>Notes</h3><P><A name="1">[1]</A><tt>Lexicographical_compare_3way</tt> is almost, but not quite, redundant:the call <tt>lexicographical_compare_3way(f1,l1, f2,l2)</tt> could be writtenas <tt><A href="lexicographical_compare.html">lexicographical_compare</A>(f1,l1, f2,l2) ? -1 :(<A href="lexicographical_compare.html">lexicographical_compare</A>(f2,l2, f1,l1) ? 1 : 0)</tt>. The single call to <tt>lexicographical_compare_3way</tt>, however, is much faster than the twocalls to <tt><A href="lexicographical_compare.html">lexicographical_compare</A></tt>.<P><A name="2">[2]</A>"Equivalent", not "equal", because two equivalent elements(that is, two elements with the property that neither one isless than the other) are not necessarily equal. <tt>Operator<</tt>is required to induce a <i>strict weak ordering</i>, not necessarilya <i>total ordering</i>. See the <A href="LessThanComparable.html">LessThan Comparable</A> requirementsfor a discussion.<h3>See also</h3><tt><A href="lexicographical_compare.html">lexicographical_compare</A></tt>,<tt><A href="equal.html">equal</A></tt>, <tt><A href="mismatch.html">mismatch</A></tt>, <tt><A href="search.html">search</A></tt>,<A href="LessThanComparable.html">LessThan Comparable</A>, <A href="StrictWeakOrdering.html">Strict Weak Ordering</A>, <tt><A href="sort.html">sort</A></tt><!-- start footer --><!-- Footer Begins --><STYLE TYPE="text/css"><!--TD.footer, TD.footer A{ font-family: Arial, helvetica, sans-serif; font-size: 8pt;}A.home {font-family: Arial, helvetica, sans-serif;}--></STYLE><P><A CLASS="home" HREF="index.html">STL Home</A><P><TABLE WIDTH="600" CELLPADDING="0" CELLPADDING="0" BORDER="0"> <TR> <TD ALIGN="RIGHT" CLASS="footer"><A HREF="/company_info/terms.html" TARGET="_top">terms of use</A> | <A HREF="/company_info/privacy.html" TARGET="_top">privacy policy</A></TD> <TD ALIGN="CENTER" CLASS="footer"> | </TD> <TD ALIGN="LEFT" CLASS="footer"><A HREF="/cgi-bin/feedback/" TARGET="_top">contact us</A></TD> </TR><TR> <TD ALIGN="RIGHT" CLASS="footer">Copyright © 1993-2003 Silicon Graphics, Inc. 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