copy

Artikel
07/29/2015

Assigns the values of elements from a source range to a destination range, iterating through the source sequence of elements and assigning them new positions in a forward direction.

template<class InputIterator, class OutputIterator> 
   OutputIterator copy( 
      InputIterator _First,  
      InputIterator _Last,  
      OutputIterator _DestBeg 
   );

Parameters

_First
An input iterator addressing the position of the first element in the source range.
_Last
An input iterator addressing the position that is one past the final element in the source range.
_DestBeg
An output iterator addressing the position of the first element in the destination range.

Return Value

An output iterator addressing the position that is one past the final element in the destination range, that is, the iterator addresses _Result + (_Last – _First ).

Remarks

The source range must be valid and there must be sufficient space at the destination to hold all the elements being copied.

Because the algorithm copies the source elements in order beginning with the first element, the destination range can overlap with the source range provided the _Last position of the source range is not contained in the destination range. copy can be used to shift elements to the left but not the right, unless there is no overlap between the source and destination ranges. To shift to the right any number of positions, use the copy_backward algorithm.

The copy algorithm only modifies values pointed to by the iterators, assigning new values to elements in the destination range. It cannot be used to create new elements and cannot insert elements into an empty container directly.

copy has two related forms:

For information on how these functions behave, see Checked Iterators.

Example

// alg_copy.cpp
// compile with: /EHsc
#include <vector>
#include <algorithm>
#include <iostream>

int main() {
   using namespace std;
   vector <int> v1, v2;
   vector <int>::iterator Iter1, Iter2;

   int i;
   for ( i = 0 ; i <= 5 ; i++ )
      v1.push_back( 10 * i );

   int ii;
   for ( ii = 0 ; ii <= 10 ; ii++ )
      v2.push_back( 3 * ii );

   cout << "v1 = ( " ;
   for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )
      cout << *Iter1 << " ";
   cout << ")" << endl;

   cout << "v2 = ( " ;
   for ( Iter2 = v2.begin( ) ; Iter2 != v2.end( ) ; Iter2++ )
      cout << *Iter2 << " ";
   cout << ")" << endl;

   // To copy the first 3 elements of v1 into the middle of v2
   copy( v1.begin( ), v1.begin( ) + 3, v2.begin( ) + 4 );

   cout << "v2 with v1 insert = ( " ;
   for ( Iter2 = v2.begin( ) ; Iter2 != v2.end( ) ; Iter2++ )
      cout << *Iter2 << " ";
   cout << ")" << endl;

   // To shift the elements inserted into v2 two positions
   // to the left
   copy( v2.begin( )+4, v2.begin( ) + 7, v2.begin( ) + 2 );

   cout << "v2 with shifted insert = ( " ;
   for ( Iter2 = v2.begin( ) ; Iter2 != v2.end( ) ; Iter2++ )
      cout << *Iter2 << " ";
   cout << ")" << endl;
}

For another sample showing how to use copy, see accumulate, copy, and vector::push_back.

v1 = ( 0 10 20 30 40 50 )
v2 = ( 0 3 6 9 12 15 18 21 24 27 30 )
v2 with v1 insert = ( 0 3 6 9 0 10 20 21 24 27 30 )
v2 with shifted insert = ( 0 3 0 10 20 10 20 21 24 27 30 )

Output

v1 = ( 0 10 20 30 40 50 )
v2 = ( 0 3 6 9 12 15 18 21 24 27 30 )
v2 with v1 insert = ( 0 3 6 9 0 10 20 21 24 27 30 )
v2 with shifted insert = ( 0 3 0 10 20 10 20 21 24 27 30 )

Requirements

Header: <algorithm>

Namespace: std

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