< cpp‎ | experimental‎ | ranges
Technical Specification
Filesystem library (filesystem TS)
Library fundamentals (library fundamentals TS)
Library fundamentals 2 (library fundamentals TS v2)
Library fundamentals 3 (library fundamentals TS v3)
Extensions for parallelism (parallelism TS)
Extensions for parallelism 2 (parallelism TS v2)
Extensions for concurrency (concurrency TS)
Extensions for concurrency 2 (concurrency TS v2)
Concepts (concepts TS)
Ranges (ranges TS)
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Pattern Matching
Linear Algebra
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Metaprogramming and type traits
Tagged pairs and tuples
tag specifiers
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)
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.


[edit] Member types

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

[edit] Member functions

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


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));.

[edit] 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.

[edit] Example

[edit] See also

function object implementing x != y
(class template) [edit]