Returns true if this outcome does not compare equal to the other result. Comparison is done using operator!= on value_type or error_type if the currently chosen state is the same for both outcome and result, otherwise true is returned. Note that an excepted outcome is always unequal to a result.

Requires: operator!= must be a valid expression between value_type and A, and between error_type and B. If value_type is void, then so must be A; similarly for error_type and B.

Complexity: Whatever the underlying operator!= have. Constexpr and noexcept of underlying operations is propagated.

Guarantees: None.