# std::experimental::ranges::not_equal_to

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< cpp‎ | experimental‎ | ranges

Defined in header `<experimental/ranges/functional>` |  |
template< class T = void > requires EqualityComparable <T> || Same <T, void> || /* == on two const T lvalues invokes a built-in operator comparing pointers */ struct not_equal_to; |  | (ranges TS)
template <> struct not_equal_to<void>; |  | (ranges TS)

Function object for performing comparisons. The primary template invokes operator == on const lvalues of type `T` and negates the result. The specialization `not_equal_to<void>` deduces the parameter types of the function call operator from the arguments (but not the return type).

All specializations of `not_equal_to` are `Semiregular`.

### Member types

Member type | Definition
`is_transparent` (member only of `not_equal_to<void>` specialization) | /* unspecified */

### Member functions

operator() | checks if the arguments are not equal (public member function)

## std::experimental::ranges::not_equal_to::operator()

constexpr bool operator()(const T& x, const T& y) const; | (1) | (member only of primary `not_equal_to<T>` template)
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; | (2) | (member only of `not_equal_to<void>` specialization)

1) Compares `x` and `y`. Equivalent to return ! ranges::equal_to <>{}(x, y);
2) Compares `t` and `u`. Equivalent to return ! ranges::equal_to <>{}( std::forward <T>(t), std::forward <U>(u));.

### Notes

Unlike std::not_equal_to, `ranges::not_equal_to` requires both `==` and `!=` to be valid (via the `EqualityComparable` and `EqualityComparableWith` constraints), and is entirely defined in terms of 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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