std::experimental::ranges::EqualityComparable, std::experimental::ranges::
Defined in header <experimental/ranges/concepts>
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template
<
class T >
concept bool EqualityComparable = WeaklyEqualityComparableWith<T, T> ; |
(1) | (ranges TS) |
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template
<
class T, class U >
concept bool EqualityComparableWith =
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(2) | (ranges TS) |
EqualityComparable<T> specifies that the comparison operators == and != on T reflects equality: == yields true
EqualityComparable<T> is satisfied only if, given objects a and b of type T, bool(a == b) is true if and only if a and b are equal. Together with the requirement that a == b is equality preserving, this implies that == is symmetric and transitive, and further that == is reflexive for all objects a
EqualityComparableWith<T, U> specifies that the comparison operators == and != on (possibly mixed) T and U
EqualityComparableWith<T, U> is satisfied only if, given any lvalue t of type
const
std::remove_reference_t
<T>
and any lvalue u of type
const
std::remove_reference_t
<U>
, and let C be
ranges::common_reference_t
<
const
std::remove_reference_t
<T>
&, const
std::remove_reference_t
<U>
&
>
,
bool
(t == u)
==
bool
(C(t)
== C(u)
)
Equality preservation
An expression is equality preserving if it results in equal outputs given equal inputs.
- The inputs to an expression consist of its operands.
- The outputs of an expression consist of its result and all operands modified by the expression (if any).
Every expression required to be equality preserving is further required to be stable
Implicit expression variations
A requires-expression implicit expression variations