Standard C++ Library
Copyright 1998, Rogue Wave Software, Inc.
NAME
copy, copy_backward
- Copies a range of elements.
SYNOPSIS
#include <algorithm>
template <class InputIterator, class OutputIterator>
OutputIterator copy(InputIterator first,
InputIterator last,
OutputIterator result);
template <class BidirectionalIterator1,
class BidirectionalIterator2>
BidirectionalIterator2
copy_backward(BidirectionalIterator1 first,
BidirectionalIterator1 last,
BidirectionalIterator2 result);
DESCRIPTION
The copy algorithm copies values from the range specified by
[first, last) to the range specified by [result, result +
(last - first)). copy can be used to copy values from one
container to another, or to copy values from one location in
a container to another location in the same container, as
long as result is not within the range [first-last). copy
returns result + (last - first). For each non-negative
integer n < (last - first), copy assigns *(first + n) to
*(result + n). The result of copy is undefined if result is
in the range [first, last).
Unless result is an insert iterator, copy assumes that at
least as many elements follow result as are in the range
[first, last).
The copy_backward algorithm copies elements in the range
specified by [first, last) into the range specified by
[result - (last - first), result), starting from the end of
the sequence (last-1) and progressing to the front (first).
Note that copy_backward does not reverse the order of the
elements, it simply reverses the order of transfer.
copy_backward returns result - (last - first). You should
use copy_backward instead of copy when last is in the range
[result - (last - first), result). For each positive integer
n <= (last - first), copy_backward assigns *(last - n) to
*(result - n). The result of copy_backward is undefined if
result is in the range [first, last).
Unless result is an insert iterator, copy_backward assumes
that there are at least as many elements ahead of result as
are in the range [first, last).
COMPLEXITY
Both copy_and copy_backward perform exactly last - first
assignments.
EXAMPLE
//
// stdlib/examples/manual/copyex.cpp
//
#include <algorithm>
#include <vector>
#include <iostream>
using namespace std;
int main()
{
int d1[4] = {1,2,3,4};
int d2[4] = {5,6,7,8};
// Set up three vectors
//
vector<int> v1(d1,d1 + 4), v2(d2,d2 + 4), v3(d2,d2 + 4);
//
// Set up one empty vector
//
vector<int> v4;
//
// Copy v1 to v2
//
copy(v1.begin(),v1.end(),v2.begin());
//
// Copy backwards v1 to v3
//
copy_backward(v1.begin(),v1.end(),v3.end());
//
// Use insert iterator to copy into empty vector
//
copy(v1.begin(),v1.end(),back_inserter(v4));
//
// Copy all four to cout
//
ostream_iterator<int,char> out(cout," ");
copy(v1.begin(),v1.end(),out);
cout << endl;
copy(v2.begin(),v2.end(),out);
cout << endl;
copy(v3.begin(),v3.end(),out);
cout << endl;
copy(v4.begin(),v4.end(),out);
cout << endl;
return 0;
}
Program Output
1 2 3 4
1 2 3 4
1 2 3 4
1 2 3 4
WARNINGS
If your compiler does not support default template parame-
ters, then you always need to supply the Allocator template
argument. For instance, you have to write:
vector <int, allocator<int> >
instead of:
vector <int>
If your compiler does not support namespaces, then you do
not need the using declaration for std.