std::experimental::ranges::not_equal_to

< 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