# 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.

### See also

Allocators, `construct`, `destroy`, `uninitialized_fill`, `uninitialized_fill_n`, `raw_storage_iterator`

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