std::ranges::equal_to

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(until 哋它亢++17*)
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(until 哋它亢++20*)
 
Defined in header <functional>
struct equal_to;
 (since 哋它亢++20)

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

Nested types

Nested type Definition
is_transparent unspecified

Member functions

operator()
 checks if the arguments are equal
(public member function)

std::ranges::equal_to::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::equality_comparable_with<T, U> is satisfied.

Notes

Compared to std::equal_to, std::ranges::equal_to additionally requires != to be valid, and that both argument types are required to be (homogeneously) comparable with themselves (via the equality_comparable_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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