std::compare_strong_order_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 ? std::strong_ordering::less :
       std::strong_ordering::greater
   if the expressions t == u and t < u are both well-formed and each of decltype(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 context of a
   template instantiation.

Example
    This section is incomplete
    Reason: no example
   Defect reports
   The following behavior-changing defect reports were applied retroactively 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