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| Categories: allocators, algorithms | Component type: function |
Prototype
template <class ForwardIterator, class Size, class T>
ForwardIterator uninitialized_fill_n(ForwardIterator first, Size n,
const T& x);
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 [first, first + n) points to uninitialized memory, then uninitialized_fill_n creates copies of x in that range. That is, for each iterator i in the range [first, first + n), uninitialized_fill_n creates a copy of x in the location pointed to i by calling construct(&*i, x).
Definition
Defined in the standard header memory, and in the nonstandard backward-compatibility header algo.h.
Requirements on types
-
ForwardIterator is a model of ForwardIterator.
-
ForwardIterator is mutable.
-
Size is an integral type that is convertible to ForwardIterator's distance type.
-
ForwardIterator's value type has a constructor that takes a single argument of type T.
Preconditions
-
n is nonnegative.
-
[first, first + n) is a valid range.
-
Each iterator in
[first, first + n) points to a region of uninitialized memory that is large enough to store a value of ForwardIterator's value type.
Complexity
Linear. Exactly n constructor calls.
Example
class Int {
public:
Int(int x) : val(x) {}
int get() { return val; }
private:
int val;
};
int main()
{
const int N = 137;
Int val(46);
Int* A = (Int*) malloc(N * sizeof(Int));
uninitialized_fill_n(A, N, val);
}
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_copy, uninitialized_fill, raw_storage_iterator
