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<HTML><!-- -- Copyright (c) 1996-1999 -- Silicon Graphics Computer Systems, Inc. -- -- Permission to use, copy, modify, distribute and sell this software -- and its documentation for any purpose is hereby granted without fee, -- provided that the above copyright notice appears in all copies and -- that both that copyright notice and this permission notice appear -- in supporting documentation. Silicon Graphics makes no -- representations about the suitability of this software for any -- purpose. It is provided "as is" without express or implied warranty. -- -- Copyright (c) 1994 -- Hewlett-Packard Company -- -- Permission to use, copy, modify, distribute and sell this software -- and its documentation for any purpose is hereby granted without fee, -- provided that the above copyright notice appears in all copies and -- that both that copyright notice and this permission notice appear -- in supporting documentation. Hewlett-Packard Company makes no -- representations about the suitability of this software for any -- purpose. It is provided "as is" without express or implied warranty. -- --><Head><Title>pair<T1, T2></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>pair<T1, T2></H1><Table CellPadding=0 CellSpacing=0 width=100%><TR><TD Align=left><Img src = "utilities.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD><TD Align=right><Img src = "type.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD></TR><TR><TD Align=left VAlign=top><b>Category</b>: utilities</TD><TD Align=right VAlign=top><b>Component type</b>: type</TD></TR></Table><h3>Description</h3><tt>Pair<T1,T2></tt> is a heterogeneous pair: it holds one object of type <tt>T1</tt> and one of type <tt>T2</tt>. A pair is much like a <A href="Container.html">Container</A>,in that it "owns" its elements. It is not actually a model of<A href="Container.html">Container</A>, though, because it does not support the standardmethods (such as <A href="Iterators.html">iterators</A>) for accessing the elements of a<A href="Container.html">Container</A>.<P>Functions that need to return two values often return a <tt>pair</tt>.<h3>Example</h3><pre>pair<bool, double> result = do_a_calculation();if (result.first) do_something_more(result.second);else report_error();</pre><h3>Definition</h3>Defined in the standard header <A href="utility">utility</A>, and in the nonstandardbackward-compatibility header <A href="pair.h">pair.h</A>.<h3>Template parameters</h3><Table border><TR><TH>Parameter</TH><TH>Description</TH><TH>Default</TH></TR><TR><TD VAlign=top><tt>T1</tt></TD><TD VAlign=top>The type of the first element stored in the <tt>pair</tt></TD><TD VAlign=top> </TD></TR><TR><TD VAlign=top><tt>T2</tt></TD><TD VAlign=top>The type of the second element stored in the <tt>pair</tt></TD><TD VAlign=top> </TD></tr></table><h3>Model of</h3><A href="Assignable.html">Assignable</A><h3>Type requirements</h3><tt>T1</tt> and <tt>T2</tt> must both be models of <A href="Assignable.html">Assignable</A>. Additional operationshave additional requirements. <tt>Pair</tt>'s default constructor may onlybe used if both <tt>T1</tt> and <tt>T2</tt> are <A href="DefaultConstructible.html">DefaultConstructible</A>, <tt>operator==</tt> may only be used if both <tt>T1</tt> and <tt>T2</tt> are<A href="EqualityComparable.html">EqualityComparable</A>, and <tt>operator<</tt> may only be used if both<tt>T1</tt> and <tt>T2</tt> are <A href="LessThanComparable.html">LessThanComparable</A>.<h3>Public base classes</h3>None.<h3>Members</h3><Table border><TR><TH>Member</TH><TH>Where defined</TH><TH>Description</TH></TR><TR><TD VAlign=top><tt>first_type</tt></TD><TD VAlign=top><tt>pair</tt></TD><TD VAlign=top>See below.</TD></TR><TR><TD VAlign=top><tt>second_type</tt></TD><TD VAlign=top><tt>pair</tt></TD><TD VAlign=top>See below.</TD></TR><TR><TD VAlign=top><tt>pair()</tt></TD><TD VAlign=top><tt>pair</tt></TD><TD VAlign=top>The default constructor. See below.</TD></TR><TR><TD VAlign=top><tt>pair(const first_type&, const second_type&)</tt></TD><TD VAlign=top><tt>pair</tt></TD><TD VAlign=top>The pair constructor. See below.</TD></TR><TR><TD VAlign=top><tt>pair(const pair&)</tt></TD><TD VAlign=top> <A href="Assignable.html">Assignable</A></TD><TD VAlign=top>The copy constructor</TD></TR><TR><TD VAlign=top><tt>pair& operator=(const pair&)</tt></TD><TD VAlign=top> <A href="Assignable.html">Assignable</A></TD><TD VAlign=top>The assignment operator</TD></TR><TR><TD VAlign=top><tt>first</tt></TD><TD VAlign=top><tt>pair</tt></TD><TD VAlign=top>See below.</TD></TR><TR><TD VAlign=top><tt>second</tt></TD><TD VAlign=top><tt>pair</tt></TD><TD VAlign=top>See below.</TD></TR><TR><TD VAlign=top><tt>bool operator==(const pair&, const pair&)</tt></TD><TD VAlign=top><tt>pair</tt></TD><TD VAlign=top>See below.</TD></TR><TR><TD VAlign=top><tt>bool operator<(const pair&, const pair&)</tt></TD><TD VAlign=top><tt>pair</tt></TD><TD VAlign=top>See below.</TD></TR><TR><TD VAlign=top><pre>template <class T1, class T2>pair<T1, T2> make_pair(const T1&, const T2&)</pre></TD><TD VAlign=top><tt>pair</tt></TD><TD VAlign=top>See below.</TD></tr></table><h3>New members</h3>These members are not defined in the <A href="Assignable.html">Assignable</A> requirements,but are specific to <tt>pair</tt>.<Table border><TR><TH>Member</TH><TH>Description</TH></TR><TR><TD VAlign=top><tt>first_type</tt></TD><TD VAlign=top>The type of the pair's first component. This is a <tt>typedef</tt> for the template parameter <tt>T1</tt></TD></TR><TR><TD VAlign=top><tt>second_type</tt></TD><TD VAlign=top>The type of the pair's second component. This is a <tt>typedef</tt> for the template parameter <tt>T2</tt></TD></TR><TR><TD VAlign=top><tt>pair()</tt></TD><TD VAlign=top>The default constructor. It uses constructs objects of types <tt>T1</tt> and <tt>T2</tt> using their default constructors. This constructor may only be used if both <tt>T1</tt> and <tt>T2</tt> are <A href="DefaultConstructible.html">DefaultConstructible</A>.</TD></TR><TR><TD VAlign=top><tt>pair(const first_type& x, const second_type& y)</tt></TD><TD VAlign=top>The pair constructor. Constructs a pair such that <tt>first</tt> is constructed from <tt>x</tt> and <tt>second</tt> is constructed from <tt>y</tt>.</TD></TR><TR><TD VAlign=top><tt>first</tt></TD><TD VAlign=top>Public member variable of type <tt>first_type</tt>: the first object stored in the <tt>pair</tt>.</TD></TR><TR><TD VAlign=top><tt>second</tt></TD><TD VAlign=top>Public member variable of type <tt>second_type</tt>: The second object stored in the <tt>pair</tt>.</TD></TR><TR><TD VAlign=top><pre>template <class T1, class T2>bool operator==(const pair<T1,T2>& x, const pair<T1,T2>& y);</pre></TD><TD VAlign=top>The equality operator. The return value is <tt>true</tt> if and only the first elements of <tt>x</tt> and <tt>y</tt> are equal, and the secondelements of <tt>x</tt> and <tt>y</tt> are equal. This operator may onlybe used if both <tt>T1</tt> and <tt>T2</tt> are <A href="EqualityComparable.html">EqualityComparable</A>.This is a global function, not a member function.</TD></TR><TR><TD VAlign=top><pre>template <class T1, class T2>bool operator<(const pair<T1,T2>& x, const pair<T1,T2>& y);</pre></TD><TD VAlign=top>The comparison operator. It uses lexicographic comparison:the return value is <tt>true</tt> if thefirst element of <tt>x</tt> is less than the first element of <tt>y</tt>,and <tt>false</tt> if the first element of <tt>y</tt> is less than the firstelement of <tt>x</tt>. If neither of these is the case, then<tt>operator<</tt> returns the result of comparing the second elementsof <tt>x</tt> and <tt>y</tt>. This operator may onlybe used if both <tt>T1</tt> and <tt>T2</tt> are <A href="LessThanComparable.html">LessThanComparable</A>.This is a global function, not a member function.</TD></TR><TR><TD VAlign=top><pre>template <class T1, class T2>pair<T1, T2> make_pair(const T1& x, const T2& x)</pre></TD><TD VAlign=top>Equivalent to <tt>pair<T1, T2>(x, y)</tt>.This is a global function, not a member function.It exists only for the sake of convenience.</TD></tr></table><h3>Notes</h3><h3>See also</h3><A href="Assignable.html">Assignable</A>, <A href="DefaultConstructible.html">Default Constructible</A>, <A href="LessThanComparable.html">LessThan Comparable</A><!-- 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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