NAME

std::experimental::ranges::not_equal_to - std::experimental::ranges::not_equal_to

Synopsis

Defined in header <experimental/ranges/functional>
template< class T = void >

requires EqualityComparable<T> ||
Same<T, void> || (ranges TS)
/* == on two const T lvalues invokes a built-in operator comparing
pointers */

struct not_equal_to;
template <> (ranges TS)
struct not_equal_to<void>;

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 (1) (member only of primary
T& y) const; not_equal_to<T> template)
template< class T, class U >

requires EqualityComparableWith<T, U> ||
/* std::declval<T>() == std::declval<U>() (member only of not_equal_to<void>
resolves to (2) specialization)
a built-in operator comparing pointers */

constexpr bool operator()(T&& t, U&& u)
const;

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