template <InputIterator I1, Sentinel<I1> S1, InputIterator I2, Sentinel<I2> S2,
WeaklyIncrementable O, class Comp = less<>, class Proj1 = identity, class Proj2 = identity>
requires Mergeable<I1, I2, O, Comp, Proj1, Proj2>
tagged_pair<tag::in1(I1), tag::out(O)>
set_difference(I1 first1, S1 last1, I2 first2, S2 last2, O result,
Comp comp = Comp{}, Proj1 proj1 = Proj1{}, Proj2 proj2 = Proj2{});
template <InputRange Rng1, InputRange Rng2, WeaklyIncrementable O,
class Comp = less<>, class Proj1 = identity, class Proj2 = identity>
requires Mergeable<iterator_t<Rng1>, iterator_t<Rng2>, O, Comp, Proj1, Proj2>
tagged_pair<tag::in1(safe_iterator_t<Rng1>), tag::out(O)>
set_difference(Rng1&& rng1, Rng2&& rng2, O result,
Comp comp = Comp{}, Proj1 proj1 = Proj1{}, Proj2 proj2 = Proj2{});
Effects: Copies the elements of the range [first1,last1) which are not present in the range [first2,last2) to the range beginning at result. The elements in the constructed range are sorted.
Requires: The resulting range shall not overlap with either of the original ranges.
Returns: {last1, result + n}, where n is the number of elements in the constructed range.
Complexity: At most 2 * ((last1 - first1) + (last2 - first2)) - 1 applications of the comparison function and projections.
Remarks: If [first1,last1) contains m elements that are equivalent to each other and [first2,last2) contains n elements that are equivalent to them, the last max(m - n, 0) elements from [first1,last1) shall be copied to the output range.