# std::ranges::not_equal_to

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< cpp‎ | utility‎ | functional

Defined in header `<functional>` |  |
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).

### 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 EqualityComparableWith <T, U> || /* std::declval<T>() == std::declval<U>() resolves to a built-in operator comparing pointers */ constexpr bool operator()(T&& t, U&& u) const; |  |

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 `EqualityComparableWith` constraint), and is entirely defined in terms of std::ranges::equal_to. However, the implementation is free to use operator!= directly, because those concepts require the results of `==` and `!=` to be consistent.

### Example

| This section is incomplete Reason: no example

### See also

not_equal_to | function object implementing x != y (class template)

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