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<HTML>
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<HEAD>
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<TITLE>front_insert_iterator, front_inserter()</TITLE>
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<LINK REL=StyleSheet HREF="../rw.css" TYPE="text/css" TITLE="Apache stdcxx Stylesheet"></HEAD>
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<BODY BGCOLOR=#FFFFFF>
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<A HREF="fpos.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="fstream-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>front_insert_iterator, front_inserter()</H2>
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<P><B>Library:</B> <A HREF="2-8.html">Iterators</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">Interface</A></LI>
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<LI><A HREF="#sec6">Member Types</A></LI>
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<LI><A HREF="#sec7">Constructors</A></LI>
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<LI><A HREF="#sec8">Operators</A></LI>
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<LI><A HREF="#sec9">Nonmember Functions</A></LI>
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<LI><A HREF="#sec10">Example</A></LI>
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<LI><A HREF="#sec11">See Also</A></LI>
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<LI><A HREF="#sec12">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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<H4>Members</H4>
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<UL><TABLE CELLPADDING=3>
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<TR><TD VALIGN=top>
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<A HREF="#idx641">container_type</A><BR>
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<A HREF="#idx642">front_insert_iterator()</A><BR>
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</TD>
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<TD VALIGN=top><A HREF="#idx644">operator*()</A><BR>
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<A HREF="#idx645">operator++()</A><BR>
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</TD>
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<TD VALIGN=top><A HREF="#idx643">operator=()</A><BR>
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</TD></TR>
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</TABLE></UL>
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<H4>Non-Members</H4>
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<UL><TABLE CELLPADDING=3>
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<TR><TD VALIGN=top>
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<A HREF="#idx646">front_inserter()</A><BR>
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</TD>
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<TD VALIGN=top></TD></TR>
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</TABLE></UL>
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<A NAME="sec2"><H3>Summary</H3></A>
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<P>An output iterator used to insert items at the beginning of a collection</P>
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<A NAME="sec3"><H3>Synopsis</H3></A>
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<PRE>#include <iterator>
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namespace std {
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template <class Container>
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class front_insert_iterator;
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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>Insert iterators let you<I> insert</I> new elements into a collection rather than copy a new element's value over the value of an existing element. The class template <B><I><A HREF="front-insert-iterator.html">front_insert_iterator</A></I></B> is used to insert items at the beginning of a collection. The convenience function template <SAMP><A HREF="front-insert-iterator.html">front_inserter()</A></SAMP> creates an instance of a <B><I>front_insert_iterator</I></B> for a particular collection type. A <B><I>front_insert_iterator</I></B> can be used with any container that defines the <SAMP>push_front()</SAMP> member function, specifically the sequences <B><I><A HREF="deque.html">deque</A></I></B> and <B><I><A HREF="list.html">list</A></I></B>, but not with associative containers (e.g., <B><I><A HREF="map.html">map</A></I></B> or <B><I><A HREF="set.html">set</A></I></B>).</P>
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<P>Note that a <B><I><A HREF="front-insert-iterator.html">front_insert_iterator</A></I></B> makes each element that it inserts the new front of the container. This has the effect of reversing the order of the inserted elements. For example, if you use a <B><I>front_insert_iterator</I></B> to insert "1" then "2" then "3" onto the front of container <SAMP>exmpl</SAMP>, you find, after the three insertions, that the first three elements of <SAMP>exmpl</SAMP> are "3 2 1".</P>
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<A NAME="sec5"><H3>Interface</H3></A>
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<UL><PRE>namespace std {
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template <class Container>
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class front_insert_iterator : public
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iterator<output_iterator_tag,void,void,void,void> {
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protected:
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Container* container;
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public:
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typedef Container container_type;
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explicit front_insert_iterator(container_tyep&);
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front_insert_iterator&
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operator=(typename container_type::const_reference&);
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front_insert_iterator& operator*();
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front_insert_iterator& operator++();
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front_insert_iterator operator++(int);
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};
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template <class Container>
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front_insert_iterator<Container>
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front_inserter(Container&);
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}
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</PRE></UL>
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<A NAME="sec6"><H3>Member Types</H3></A>
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<A NAME="idx641"></A><PRE><B>container_type</B></PRE>
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<UL>
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<P>The type of container acted on by this iterator.</P>
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</UL>
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<A NAME="sec7"><H3>Constructors</H3></A>
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<A NAME="idx642"></A><PRE>explicit
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<B>front_insert_iterator</B>(container_type& x);</PRE>
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<UL>
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<P>Creates an instance of a <B><I><A HREF="front-insert-iterator.html">front_insert_iterator</A></I></B> associated with container <SAMP>x.</SAMP></P>
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</UL>
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<A NAME="sec8"><H3>Operators</H3></A>
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<A NAME="idx643"></A><PRE>front_insert_iterator<Container>&
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<B>operator=</B>(typename container_type::constant_reference &value);</PRE>
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<UL>
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<P>Inserts a copy of <SAMP>value</SAMP> at the front of the container by calling <SAMP>container->push_front (value)</SAMP>, and returns <SAMP>*this</SAMP>.</P>
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</UL>
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<A NAME="idx644"></A><PRE>front_insert_iterator&
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<B>operator*</B>();</PRE>
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<UL>
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<P>Returns <SAMP>*this</SAMP> (the iterator itself).</P>
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</UL>
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<A NAME="idx645"></A><PRE>front_insert_iterator&
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<B>operator++</B>();
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front_insert_iterator
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<B>operator++</B>(int);</PRE>
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<UL>
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<P>Increments the insert iterator and returns <SAMP>*this</SAMP>.</P>
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</UL>
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<A NAME="sec9"><H3>Nonmember Functions</H3></A>
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<A NAME="idx646"></A><PRE>template <class Container>
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front_insert_iterator<Container>
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<B>front_inserter</B>(Container& x)</PRE>
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<UL>
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<P>Returns a <B><I><A HREF="front-insert-iterator.html">front_insert_iterator</A></I></B> that inserts elements at the beginning of container <SAMP>x</SAMP>.</P>
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</UL>
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<A NAME="sec10"><H3>Example</H3></A>
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<UL><PRE>//
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// ins_itr.cpp
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//
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#include <algorithm> // for copy
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#include <iostream> // for cout, endl
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#include <iterator> // for ostream_iterator, xxx_inserter
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#include <deque> // for deque
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int main ()
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{
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// Typedefs for convenience.
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typedef std::deque<int, std::allocator<int> > Deque;
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typedef std::ostream_iterator<int, char,
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std::char_traits<char> > os_iter;
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// Initialize a deque using an array.
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Deque::value_type arr[] = { 3, 4, 7, 8 };
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Deque d (arr, arr + sizeof arr / sizeof *arr);
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// Output the original deque.
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std::cout << "Start with a deque: \n ";
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std::copy (d.begin (), d.end (), os_iter (std::cout, " "));
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// Insert into the middle.
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std::insert_iterator<Deque> ins (d, d.begin () + 2);
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*ins = 5;
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*ins = 6;
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// Output the new deque.
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std::cout << "\n\nUse an insert_iterator: \n ";
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std::copy (d.begin (), d.end (), os_iter (std::cout, " "));
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// A deque of four 1s.
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Deque d2 (4, 1);
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// Insert d2 at front of d.
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std::copy (d2.begin (), d2.end (),
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std::front_inserter (d));
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// Output the new deque.
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std::cout << "\n\nUse a front_inserter: \n ";
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std::copy (d.begin (), d.end (), os_iter (std::cout, " "));
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// Insert d2 at back of d.
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std::copy (d2.begin (), d2.end (), std::back_inserter (d));
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// Output the new deque.
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std::cout << "\n\nUse a back_inserter: \n ";
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std::copy (d.begin (), d.end (), os_iter (std::cout, " "));
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std::cout << 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>Start with a deque:
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3 4 7 8
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Use an insert_iterator:
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3 4 5 6 7 8
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Use a front_inserter:
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1 1 1 1 3 4 5 6 7 8
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Use a back_inserter:
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1 1 1 1 3 4 5 6 7 8 1 1 1 1
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</PRE></UL>
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<A NAME="sec11"><H3>See Also</H3></A>
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<P><A HREF="insertiterators.html">Insert Iterators</A></P>
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<A NAME="sec12"><H3>Standards Conformance</H3></A>
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<P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 24.4.2.3</I></P>
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<BR>
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<HR>
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