<xstd/bits/bit_algorithm/bit_set_union.hpp>, <xstd/bits/bit_algorithm/bit_set_intersection.hpp>, <xstd/bits/bit_algorithm/bit_set_difference.hpp>, <xstd/bits/bit_algorithm/bit_set_symmetric_difference.hpp>

bit_set_union, bit_set_intersection, bit_set_difference, bit_set_symmetric_difference

As ranges::set_union, ranges::set_intersection, ranges::set_difference and ranges::set_symmetric_difference in [set.union], [set.intersection], [set.difference] and [set.symmetric.difference], returning the set rather than writing through an output iterator, with:

• Constraints: S is a set of ours whose operator |, &, - or ^ respectively answers an S: an owner. A view, which has no result to hold, is turned away. s2 converts to S, as for bit_includes.
• Returns: s1 | s2, s1 & s2, s1 - s2 and s1 ^ s2: the set that range-v3's views::set_union(s1, s2, s1.key_comp()) and its siblings would hold, of the first argument's type, whatever widths held the keys.
• Complexity: That of the operator.
• Remarks: The exception specification is noexcept(declval<const S&>() | declval<const S&>()), with the operator each one calls.