unique_copy

template<class InIt, class OutIt>
    OutIt unique_copy(InIt first, InIt last, OutIt x);
template<class InIt, class OutIt, class Pred>
    OutIt unique_copy(InIt first, InIt last, OutIt x,
        Pred pr);

The first template function effectively executes the statement:

if (N == 0 || !(*(first + N) == V))
    V = *(first + N), *x++ = V;

once for each N in the range [0, last - first). It then returns x. Thus, the function repeatedly removes from the sequence it copies the second of a pair of elements for which the predicate *(first + N) == *(first + N - 1) is true, until only the first of a sequence of equal elements survives. Here, operator== must impose an equivalence relationship between its operands. It does so without altering the relative order of remaining elements, and returns the iterator value that designates the end of the copied sequence.

If x and first designate regions of storage, the range [x, x + (last - first)) must not overlap the range [first, last).

The second template function behaves the same, except that it executes the statement:

if (N == 0 || !pr(*(first + N), V))
    V = *(first + N), *x++ = V;