51 template(
typename I,
typename B,
typename C =
less,
typename P =
identity)(
52 requires same_as<iter_common_reference_t<I>,
53 iter_common_reference_t<B>> AND
55 I operator()(I begin0,
56 iter_difference_t<I> n0,
58 iter_difference_t<I> n1,
63 copy_n(begin0, n0, buff);
64 return merge_n(buff, n0, begin1, n1, begin0, r, p, p).out;