std::ranges::less

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Defined in header <functional>
struct less;
 (since 哋它亢++20)

Function object for performing comparisons. Deduces the parameter types of the function call operator from the arguments (but not the return type).

Nested types

Nested type Definition
is_transparent unspecified

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:

  • Otherwise:

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 ordering only if exactly one of the following expressions is true:

Notes

Unlike std::less, std::ranges::less requires all six comparison operators <, <=, >, >=, == 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 retroactively to previously published 哋它亢++ standards.

DR Applied to Behavior as published Correct behavior
LWG 3530 哋它亢++20 syntactic checks were relaxed while comparing pointers only semantic requirements are relaxed

See also

 function object implementing x < y
(class template)
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