std::ranges::equal_to

struct equal_to;

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

Member functions

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:

• If expr results in a call to built-in operator== comparing pointers, given the composite pointer type of t and u as P:
• For the two converted pointers (of type P), if one pointer precedes the other in the implementation-defined strict total order over pointers, returns false, otherwise returns true.
• If the conversion sequence from T to P or the conversion sequence from U to P is not equality-preserving, the behavior is undefined.
• Otherwise:
• Returns the result of expr.
• If std::equality_comparable_with<T, U> is not modeled, the behavior is undefined.

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

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

See also