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 + n) points to uninitialized memory, then uninitialized_copy_n creates a copy of [first, first + n) in that range. That is, for each iterator i in the input range, uninitialized_copy_n 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. This function is an SGI extension; it is not part of the C++ standard.
Requirements on types • InputIterator is a model of Input Iterator.
• Size is an integral type.
• 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 • n >= 0
• [first, first + n) is a valid range.
• [result, result + n) is a valid range.
• Each iterator in [result, result + 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() {
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_n(A1, N, A2);
}
Notes [1] In particular, this sort of low-level memory management is used in the implementation of some container classes.
[2] Uninitialized_copy_n is almost, but not quite, redundant. If first is an input iterator, as opposed to a forward iterator, then the uninitialized_copy_n operation can't be expressed in terms of uninitialized_copy.
See also Allocators, construct, destroy, uninitialized_copy, uninitialized_fill, uninitialized_fill_n, raw_storage_iterator
Categories: allocators, algorithms
Component type: function
Prototype template <class ForwardIterator, class T>
void uninitialized_fill(ForwardIterator first, ForwardIterator last, 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, last) points to uninitialized memory, then uninitialized_fill creates copies of x in that range. That is, for each iterator i in the range [first, last), uninitialized_copy 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 Forward Iterator.
• ForwardIterator is mutable.
• ForwardIterator's value type has a constructor that takes a single argument of type T.
Preconditions • [first, last) is a valid range.
• Each iterator in [first, last) 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() {
const int N = 137;
Int val(46);
Int* A = (Int*) malloc(N * sizeof(Int));
uninitialized_fill(A, A + N, val);
