std::ranges::equal_to - cppreference.com (original) (raw)

| | | | | ----------------- | | ------------- | | struct equal_to; | | (since C++20) |

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

Contents

• 1 Nested types
• 2 Member functions
• 3 std::ranges::equal_to::operator()
  • 3.1 Notes
  • 3.2 Example
  • 3.3 Defect reports
  • 3.4 See also

[edit] Nested types

[edit] Member functions

| | 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:

• 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.

[edit] 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).

[edit] Example

[edit] Defect reports

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

[edit] See also