std::ranges::not_equal_to
Defined in header <functional>
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struct not_equal_to; |
(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 arguments are not equal (public member function) |
std::ranges::not_equal_to::operator()
template< class T, class U > requires std::equality_comparable_with<T, U> // with different sematic requirements |
||
Compares t
and u
. Equivalent to return !ranges::equal_to{}(std::forward<T>(t), std::forward<U>(u));.
Notes
Unlike std::not_equal_to, std::ranges::not_equal_to
requires both ==
and !=
to be valid (via the equality_comparable_with
constraint), and is entirely defined in terms of
std::ranges::equal_to.
Example
This section is incomplete Reason: no 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 |
See also
function object implementing x != y (class template) |