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uninitialized_copy



Categories: allocators, algorithms	Component type: function

Prototype

template <class InputIterator, class ForwardIterator>
ForwardIterator uninitialized_copy(InputIterator first, InputIterator last,
                                   ForwardIterator result);

Description

In C++, the operator new allocates memory for an object and then creates an object at that location by calling a constructor. Occasionally, however, it is useful to separate those two operations. [1] If each iterator in the range [result, result + (last - first)) points to uninitialized memory, then uninitialized_copy creates a copy of [first, last) in that range. That is, for each iterator i in the input range, uninitialized_copy creates a copy of *i in the location pointed to by the corresponding iterator in the output range by calling construct(&*(result + (i - first)), *i).

Definition

Defined in the standard header memory, and in the nonstandard backward-compatibility header algo.h.

Requirements on types

InputIterator is a model of Input Iterator.
ForwardIterator is a model of Forward Iterator.
ForwardIterator is mutable.
ForwardIterator's value type has a constructor that takes a single argument whose type is InputIterator's value type.

Preconditions

[first, last) is a valid range.
[result, result + (last - first)) is a valid range.
Each iterator in [result, result + (last - first)) points to a region of uninitialized memory that is large enough to store a value of ForwardIterator's value type.

Complexity

Linear. Exactly last - first constructor calls.

Example

class Int {
public:
  Int(int x) : val(x) {}
  int get() { return val; }
private:
  int val;
};    

int main()
{
  int A1[] = {1, 2, 3, 4, 5, 6, 7};
  const int N = sizeof(A1) / sizeof(int);

  Int* A2 = (Int*) malloc(N * sizeof(Int));
  uninitialized_copy(A1, A1 + N, A2);
}

Notes

[1] In particular, this sort of low-level memory management is used in the implementation of some container classes.