Defined in header <compare> | ||
---|---|---|
class strong_equality; | (since C++20) |
The class type std::strong_equality
is the result type of a three-way comparison that.
The type std::strong_equality
has four valid values, implemented as const static data members of its type:
Member constant | Definition |
---|---|
equivalent(inline constexpr)
[static] | a valid value of the type std::strong_equality indicating equality (public static member constant) |
equal(inline constexpr)
[static] | a valid value of the type std::strong_equality indicating equality (public static member constant) |
nonequivalent(inline constexpr)
[static] | a valid value of the type std::strong_equality indicating non-equality (public static member constant) |
nonequal(inline constexpr)
[static] | a valid value of the type std::strong_equality indicating non-equality (public static member constant) |
std::strong_equality
is implicitly-convertible to std::weak_equality
, and std::strong_ordering
is implicitly-convertible to strong_equality
.
operator weak_equality | implicit conversion to std::weak_equality (public member function) |
constexpr operator weak_equality() const noexcept; |
std::weak_equality::equivalent
if v
is equivalent
or equal
, std::weak_equality::nonequivalent
if v
is nonequivalent
or nonequal
.
Comparison operators are defined between values of this type and literal 0
. This supports the expressions a <=> b == 0
and a <=> b != 0
used to convert the result of a three-way comparison operator to a boolean relationship; see std::is_eq
and std::is_neq
.
The behavior of a program that attempts to compare a strong_equality
with anything other than the integer literal 0
is undefined.
operator==operator!=operator<=> | compares with zero (function) |
friend constexpr bool operator==(strong_equality v, /*unspecified*/ u) noexcept; friend constexpr bool operator==(/*unspecified*/ u, strong_equality v) noexcept; |
v | - | a std::strong_equality value to check |
u | - | an unused parameter of any type that accepts literal zero argument |
true
if v
is equivalent
or equal
, false
if v
is nonequivalent
or nonequal
.
friend constexpr bool operator!=(strong_equality v, /*unspecified*/ u) noexcept; friend constexpr bool operator!=(/*unspecified*/ u, strong_equality v) noexcept; |
v | - | a std::strong_equality value to check |
u | - | an unused parameter of any type that accepts literal zero argument |
false
if v
is equivalent
or equal
, and true
if v
is nonequivalent
or nonequal
.
friend constexpr strong_equality operator<=>(strong_equality v, /*unspecified*/ u) noexcept; friend constexpr strong_equality operator<=>(/*unspecified*/ u, strong_equality v) noexcept; |
v | - | a std::strong_equality value to check |
u | - | an unused parameter of any type that accepts literal zero argument |
v
.
(C++20) | the result type of 3-way comparison that supports all 6 operators and is substitutable (class) |
(C++20) | the result type of 3-way comparison that supports all 6 operators and is not substitutable (class) |
(C++20) | the result type of 3-way comparison that supports all 6 operators, is not substitutable, and allows incomparable values (class) |
(C++20) | the result type of 3-way comparison that supports only equality/inequality and is not substitutable (class) |
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