std::compar...er_fallback(3) C++ Standard Libary std::compar...er_fallback(3) NAME std::compare_strong_order_fallback - std::compare_strong_order_fallback Synopsis Defined in header <compare> inline namespace /* unspecified */ { inline constexpr /* unspecified */ (since C++20) compare_strong_order_fallback = /* unspecified */; } Call signature template< class T, class U > requires /* see below */ constexpr std::strong_ordering (since C++20) compare_strong_order_fallback( T&& t, U&& u ) noexcept(/* see below */); Performs three-way comparison on subexpressions t and u and produces a result of type std::strong_ordering, even if the operator <=> is unavailable. If std::decay_t<T> and std::decay_t<U> are the same type, std::compare_strong_order_fallback(t, u) is expression-equivalent to: * std::strong_order(t, u), if it is a well-formed expression; * otherwise, t == u ? std::strong_ordering::equal : t_<_u_ _ _t_:_s_r_ng_ordering::less : a a a a a a a a a std::strong_ordering::greater if the expressions t == u and t < u are both well-formed and each of de- cltype(t == u) and decltype(t < u) models boolean-testable, except that t and u are evaluated only once. In all other cases, std::compare_strong_order_fallback(t, u) is ill- formed, which can result in substitution failure when it appears in the immediate con- text of a template instantiation. Example This section is incomplete Reason: no example Defect reports The following behavior-changing defect reports were applied retroac- tively to previously published C++ standards. DR Applied to Behavior as published Correct behavior LWG 2114 C++20 the fallback mechanism only required constraints strengthened (P2167R3) return types to be convertible to bool See also strong_order performs 3-way comparison and produces a result of type (C++20) std::strong_ordering (customization point object) Category: * Todo no example http://cppreference.com 2024.06.10 std::compar...er_fallback(3)
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