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std::ranges::less_equal

Defined in header `<functional>`
struct less_equal;		(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).

Implementation-defined strict total order over pointers

The function call operator yields the implementation-defined strict total order over pointers if the < operator between arguments invokes a built-in comparison operator for a pointer, even if the built-in < operator does not.

The implementation-defined strict total order is consistent with the partial order imposed by built-in comparison operators (<=>, <, >, <=, and >=), and consistent among following standard function objects:

std::less, std::greater, std::less_equal, and std::greater_equal, when the template argument is a pointer type or void
std::ranges::equal_to, std::ranges::not_equal_to, std::ranges::less, std::ranges::greater, std::ranges::less_equal, std::ranges::greater_equal, and std::compare_three_way

Member types

Member type	Definition
`is_transparent`	/* unspecified */

Member functions

operator()

checks if the first argument is less than or equal to the second
(public member function)

std::ranges::less_equal::operator()

template< class T, class U >
    requires std::totally_ordered_with<T, U> // with different semantic requirements
constexpr bool operator()(T&& t, U&& u) const;

Compares t and u. Equivalent to return !ranges::less{}(std::forward<U>(u), std::forward<T>(t));.

Notes

Unlike std::less_equal, std::ranges::less_equal requires all six comparison operators <, <=, >, >=, == and != to be valid (via the totally_ordered_with constraint) and is entirely defined in terms of std::ranges::less.

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 3530	C++20	syntactic checks were relaxed while comparing pointers	only semantic requirements relaxed