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154 lines
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<HEAD>
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<TITLE>copy(), copy_backward()</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="containers.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="count.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>copy(), copy_backward()</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">See Also</A></LI>
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<LI><A HREF="#sec8">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 copies a range of elements</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 InputIterator, class OutputIterator>
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OutputIterator copy(InputIterator start,
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InputIterator finish,
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OutputIterator result);
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template <class BidirectionalIterator1,
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class BidirectionalIterator2>
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BidirectionalIterator2
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copy_backward(BidirectionalIterator1 start,
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BidirectionalIterator1 finish,
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BidirectionalIterator2 result);
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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>copy()</SAMP> algorithm copies values from the range specified by <SAMP>[start</SAMP>, <SAMP>finish)</SAMP> to the range specified by <SAMP>[result, result + (finish - start))</SAMP>. <SAMP>copy()</SAMP> returns <SAMP>result + (finish - start)</SAMP>. For each non-negative integer <SAMP>n < (finish - start)</SAMP>, <SAMP>copy()</SAMP> assigns <SAMP>*(start + n)</SAMP> to <SAMP>*(result + n)</SAMP>. The result of <SAMP>copy()</SAMP> is undefined if <SAMP>result</SAMP> is in the range <SAMP>[start, finish)</SAMP>.</P>
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<P>Unless <SAMP>result</SAMP> is an insert iterator, <SAMP>copy()</SAMP> assumes that all iterators in the range <SAMP>[result + (finish - start)]</SAMP> are dereferenceable.</P>
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<P>The <SAMP><A HREF="copy.html">copy_backward()</A></SAMP> algorithm copies elements in the range specified by <SAMP>[start, finish)</SAMP> into the range specified by [<SAMP>result - (finish - start), result)</SAMP>, starting from the end of the sequence (<SAMP>finish-1</SAMP>) and progressing to the front (<SAMP>start</SAMP>). Note that <SAMP>copy_backward()</SAMP> does <I>not </I>reverse the order of the elements, it simply reverses the order of transfer. <SAMP>copy_backward()</SAMP> returns <SAMP>result - (finish - start)</SAMP>. You should use <SAMP>copy_backward()</SAMP> instead of <SAMP>copy()</SAMP> when <SAMP>finish</SAMP> is in the range <SAMP>[result - (finish - start), result)</SAMP>. For each positive integer <SAMP>n <= (finish - start)</SAMP>, <SAMP>copy_backward()</SAMP> assigns <SAMP>*(finish - n)</SAMP> to <SAMP>*(result - n)</SAMP>. The result of <SAMP>copy_backward()</SAMP> is undefined if <SAMP>result</SAMP> is in the range <SAMP>[start, finish)</SAMP>. <SAMP>copy_backward()</SAMP> should be used when <SAMP>finish</SAMP> is in the range <SAMP>[result - (finish - start), result)</SAMP>.</P>
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<P>Unless <SAMP>result</SAMP> is an insert iterator, <SAMP><A HREF="copy.html">copy_backward()</A></SAMP> assumes that all iterators in the range <SAMP>[result - (finish - start), result)</SAMP> are dereferenceable.</P>
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<A NAME="sec5"><H3>Complexity</H3></A>
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<P>Both <SAMP>copy()</SAMP> and <SAMP><A HREF="copy.html">copy_backward()</A></SAMP> perform exactly <SAMP>finish - start</SAMP> assignments.</P>
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<A NAME="sec6"><H3>Example</H3></A>
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<UL><PRE>//
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// copyex.cpp
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//
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#include <algorithm> // for copy
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#include <iostream> // for cout, endl, ostream_iterator
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#include <vector> // for vector
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int main ()
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{
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// Typedef for convenience.
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typedef std::vector<short, std::allocator<short> > vector;
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const vector::value_type d1[] = { 1, 2, 3, 4 };
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const vector::value_type d2[] = { 5, 6, 7, 8 };
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// Set up three vectors.
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vector v1(d1 + 0, d1 + 4),
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v2(d2 + 0, d2 + 4),
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v3(d2 + 0, d2 + 4);
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// Set up one empty vector.
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vector v4;
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// Copy v1 to v2.
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std::copy(v1.begin(), v1.end(), v2.begin());
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// Copy backwards v1 to v3.
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std::copy_backward(v1.begin(), v1.end(), v3.end());
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// Use insert iterator to copy into empty vector.
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std::copy(v1.begin(), v1.end(), std::back_inserter(v4));
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// Copy all four vectors to cout.
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std::ostream_iterator<vector::value_type, char,
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std::char_traits<char> > out(std::cout, " ");
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std::copy(v1.begin(), v1.end(), out);
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std::cout << std::endl;
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std::copy(v2.begin(), v2.end(), out);
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std::cout << std::endl;
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std::copy(v3.begin(), v3.end(), out);
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std::cout << std::endl;
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std::copy(v4.begin(), v4.end(), out);
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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>1 2 3 4
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1 2 3 4
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1 2 3 4
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1 2 3 4
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</PRE></UL>
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<A NAME="sec7"><H3>See Also</H3></A>
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<P><A HREF="algorithms.html">Algorithms</A>, <A HREF="algorithm-h.html"><algorithm></A></P>
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<A NAME="sec8"><H3>Standards Conformance</H3></A>
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<P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 25.2.1</I></P>
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<BR>
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