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| <H2>front_insert_iterator, front_inserter()</H2> |
| <P><B>Library:</B> <A HREF="2-8.html">Iterators</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">Interface</A></LI> |
| <LI><A HREF="#sec6">Member Types</A></LI> |
| <LI><A HREF="#sec7">Constructors</A></LI> |
| <LI><A HREF="#sec8">Operators</A></LI> |
| <LI><A HREF="#sec9">Nonmember Functions</A></LI> |
| <LI><A HREF="#sec10">Example</A></LI> |
| <LI><A HREF="#sec11">See Also</A></LI> |
| <LI><A HREF="#sec12">Standards Conformance</A></LI> |
| </UL> |
| <A NAME="sec1"><H3>Local Index</H3></A> |
| <H4>Members</H4> |
| <UL><TABLE CELLPADDING=3> |
| <TR><TD VALIGN=top> |
| <A HREF="#idx641">container_type</A><BR> |
| <A HREF="#idx642">front_insert_iterator()</A><BR> |
| </TD> |
| <TD VALIGN=top><A HREF="#idx644">operator*()</A><BR> |
| <A HREF="#idx645">operator++()</A><BR> |
| </TD> |
| <TD VALIGN=top><A HREF="#idx643">operator=()</A><BR> |
| </TD></TR> |
| </TABLE></UL> |
| <H4>Non-Members</H4> |
| <UL><TABLE CELLPADDING=3> |
| <TR><TD VALIGN=top> |
| <A HREF="#idx646">front_inserter()</A><BR> |
| </TD> |
| <TD VALIGN=top></TD></TR> |
| </TABLE></UL> |
| |
| <A NAME="sec2"><H3>Summary</H3></A> |
| <P>An output iterator used to insert items at the beginning of a collection</P> |
| <A NAME="sec3"><H3>Synopsis</H3></A> |
| |
| <PRE>#include <iterator> |
| |
| namespace std { |
| template <class Container> |
| class front_insert_iterator; |
| } |
| </PRE> |
| <A NAME="sec4"><H3>Description</H3></A> |
| <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> |
| <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> |
| <A NAME="sec5"><H3>Interface</H3></A> |
| |
| <UL><PRE>namespace std { |
| template <class Container> |
| class front_insert_iterator : public |
| iterator<output_iterator_tag,void,void,void,void> { |
| |
| protected: |
| Container* container; |
| public: |
| typedef Container container_type; |
| explicit front_insert_iterator(container_tyep&); |
| front_insert_iterator& |
| operator=(typename container_type::const_reference&); |
| front_insert_iterator& operator*(); |
| front_insert_iterator& operator++(); |
| front_insert_iterator operator++(int); |
| }; |
| |
| template <class Container> |
| front_insert_iterator<Container> |
| front_inserter(Container&); |
| } |
| </PRE></UL> |
| <A NAME="sec6"><H3>Member Types</H3></A> |
| |
| <A NAME="idx641"></A><PRE><B>container_type</B></PRE> |
| <UL> |
| <P>The type of container acted on by this iterator.</P> |
| </UL> |
| |
| <A NAME="sec7"><H3>Constructors</H3></A> |
| |
| <A NAME="idx642"></A><PRE>explicit |
| <B>front_insert_iterator</B>(container_type& x);</PRE> |
| <UL> |
| <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> |
| </UL> |
| |
| <A NAME="sec8"><H3>Operators</H3></A> |
| |
| <A NAME="idx643"></A><PRE>front_insert_iterator<Container>& |
| <B>operator=</B>(typename container_type::constant_reference &value);</PRE> |
| <UL> |
| <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> |
| </UL> |
| |
| |
| <A NAME="idx644"></A><PRE>front_insert_iterator& |
| <B>operator*</B>();</PRE> |
| <UL> |
| <P>Returns <SAMP>*this</SAMP> (the iterator itself).</P> |
| </UL> |
| |
| |
| <A NAME="idx645"></A><PRE>front_insert_iterator& |
| <B>operator++</B>(); |
| front_insert_iterator |
| <B>operator++</B>(int);</PRE> |
| <UL> |
| <P>Increments the insert iterator and returns <SAMP>*this</SAMP>.</P> |
| </UL> |
| |
| <A NAME="sec9"><H3>Nonmember Functions</H3></A> |
| |
| <A NAME="idx646"></A><PRE>template <class Container> |
| front_insert_iterator<Container> |
| <B>front_inserter</B>(Container& x)</PRE> |
| <UL> |
| <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> |
| </UL> |
| |
| <A NAME="sec10"><H3>Example</H3></A> |
| |
| <UL><PRE>// |
| // ins_itr.cpp |
| // |
| |
| #include <algorithm> // for copy |
| #include <iostream> // for cout, endl |
| #include <iterator> // for ostream_iterator, xxx_inserter |
| #include <deque> // for deque |
| |
| int main () |
| { |
| // Typedefs for convenience. |
| typedef std::deque<int, std::allocator<int> > Deque; |
| typedef std::ostream_iterator<int, char, |
| std::char_traits<char> > os_iter; |
| |
| // Initialize a deque using an array. |
| Deque::value_type arr[] = { 3, 4, 7, 8 }; |
| Deque d (arr, arr + sizeof arr / sizeof *arr); |
| |
| // Output the original deque. |
| std::cout << "Start with a deque: \n "; |
| std::copy (d.begin (), d.end (), os_iter (std::cout, " ")); |
| |
| // Insert into the middle. |
| std::insert_iterator<Deque> ins (d, d.begin () + 2); |
| *ins = 5; |
| *ins = 6; |
| |
| // Output the new deque. |
| std::cout << "\n\nUse an insert_iterator: \n "; |
| std::copy (d.begin (), d.end (), os_iter (std::cout, " ")); |
| |
| // A deque of four 1s. |
| Deque d2 (4, 1); |
| |
| // Insert d2 at front of d. |
| std::copy (d2.begin (), d2.end (), |
| std::front_inserter (d)); |
| |
| // Output the new deque. |
| std::cout << "\n\nUse a front_inserter: \n "; |
| std::copy (d.begin (), d.end (), os_iter (std::cout, " ")); |
| |
| // Insert d2 at back of d. |
| std::copy (d2.begin (), d2.end (), std::back_inserter (d)); |
| |
| // Output the new deque. |
| std::cout << "\n\nUse a back_inserter: \n "; |
| std::copy (d.begin (), d.end (), os_iter (std::cout, " ")); |
| |
| std::cout << std::endl; |
| |
| return 0; |
| } |
| |
| |
| Program Output: |
| </PRE></UL> |
| <UL><PRE>Start with a deque: |
| 3 4 7 8 |
| |
| Use an insert_iterator: |
| 3 4 5 6 7 8 |
| |
| Use a front_inserter: |
| 1 1 1 1 3 4 5 6 7 8 |
| |
| Use a back_inserter: |
| 1 1 1 1 3 4 5 6 7 8 1 1 1 1 |
| </PRE></UL> |
| <A NAME="sec11"><H3>See Also</H3></A> |
| <P><A HREF="insertiterators.html">Insert Iterators</A></P> |
| <A NAME="sec12"><H3>Standards Conformance</H3></A> |
| <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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