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std::ranges::less(3) C++ Standard Libary std::ranges::less(3) NAME std::ranges::less - std::ranges::less Synopsis Defined in header <functional> struct less; (since C++20) Function object for performing comparisons. Deduces the parameter types of the function call operator from the arguments (but not the return type). Member functions operator() checks if the first argument is less than the second (public member function) std::ranges::less::operator() template< class T, class U > constexpr bool operator()( T&& t, U&& u ) const; Given the expression std::forward<T>(t) < std::forward<U>(u) as expr: * If expr results in a call to built-in operator< comparing point- ers, given the composite pointer type of t and u as P: * If the converted t precedes the converted u (both are of type P) in the implementation-defined strict total order over pointers, returns true, otherwise returns false. * If the conversion sequence from T to P or the conversion se- quence from U to P is not equality-preserving, the behavior is undefined. * Otherwise: * Returns the result of expr. * If std::totally_ordered_with<T, U> is not modeled, the behavior is undefined. This overload participates in overload resolution only if std::totally_ordered_with<T, U> is satisfied. If there exists an expression expr1 of type T and an expression expr2 of U, such that the comparison results of expr1 and expr2 violate strict total ordering (rules are defined below), the behavior is undefined. The comparison results of expr1 and expr2 follow strict total order- ing only if exactly one of the following expressions is true: * std::ranges::less{}(expr1, expr2) * std::ranges::less{}(expr2, expr1) * std::ranges::equal_to{}(expr1, expr2) Notes Unlike std::less, std::ranges::less requires all six comparison op- erators <, <=, >, >=, == and != to be valid (via the totally_ordered_with constraint). 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 3530 C++20 syntactic checks were relaxed only semantic requirements are while comparing pointers relaxed See also less function object implementing x < y (class template) Category: * Todo no example http://cppreference.com 2024.06.10 std::ranges::less(3)
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