Difference between revisions of "cpp/utility/functional/reference wrapper/operator cmp"
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@1,2@ Compares two {{tt|reference_wrapper}} objects. The objects compare equal if and only if {{c|lhs.get()}} and {{c|rhs.get()}} are equal. | @1,2@ Compares two {{tt|reference_wrapper}} objects. The objects compare equal if and only if {{c|lhs.get()}} and {{c|rhs.get()}} are equal. | ||
| − | * | + | * Both overloads participate in overload resolution only if {{c|1=lhs.get() == rhs.get()}} is well-formed and its result is convertible to {{c|bool}}. |
| − | * The overload {{v|2}} participates in overload resolution only if {{c|std::is_const_v<T>}} is {{c|false}}. | + | * The overload {{v|2}} participates in overload resolution only if {{c|std::is_const_v<T>}} is {{c|false}}. |
@3@ Compares {{tt|reference_wrapper}} object with a reference. The parameters compare equal if and only if {{c|lhs.get()}} is equal to {{c|ref}}. | @3@ Compares {{tt|reference_wrapper}} object with a reference. The parameters compare equal if and only if {{c|lhs.get()}} is equal to {{c|ref}}. | ||
| − | * | + | * The overload {{v|3}} participates in overload resolution only if {{c|1=lhs.get() == ref}} is well-formed and its result is convertible to {{c|bool}}. |
@4,5@ Compares two {{tt|reference_wrapper}} objects as if by {{box|{{lti|cpp/standard library/synth-three-way}}{{c/core|1=(lhs.get(), rhs.get())}}}}. | @4,5@ Compares two {{tt|reference_wrapper}} objects as if by {{box|{{lti|cpp/standard library/synth-three-way}}{{c/core|1=(lhs.get(), rhs.get())}}}}. | ||
Revision as of 05:32, 19 April 2024
| friend constexpr bool operator==( reference_wrapper lhs, reference_wrapper rhs ); |
(1) | (since C++26) |
| friend constexpr bool operator==( reference_wrapper lhs, reference_wrapper<const T> rhs ); |
(2) | (since C++26) |
| friend constexpr bool operator==( reference_wrapper lhs, const T& ref ); |
(3) | (since C++26) |
| friend constexpr synth-three-way-result<T> operator<=>( reference_wrapper lhs, reference_wrapper rhs ); |
(4) | (since C++26) |
| friend constexpr synth-three-way-result<T> operator<=>( reference_wrapper lhs, reference_wrapper<const T> rhs ); |
(5) | (since C++26) |
| friend constexpr synth-three-way-result<T> operator<=>( reference_wrapper lhs, const T& ref ); |
(6) | (since C++26) |
Performs comparison operations on reference_wrapper objects.
1,2) Compares two
reference_wrapper objects. The objects compare equal if and only if lhs.get() and rhs.get() are equal.
- Both overloads participate in overload resolution only if lhs.get() == rhs.get() is well-formed and its result is convertible to bool.
- The overload (2) participates in overload resolution only if std::is_const_v<T> is false.
3) Compares
reference_wrapper object with a reference. The parameters compare equal if and only if lhs.get() is equal to ref.
- The overload (3) participates in overload resolution only if lhs.get() == ref is well-formed and its result is convertible to bool.
4,5) Compares two
reference_wrapper objects as if by synth-three-way(lhs.get(), rhs.get()).
- The overload (5) participates in overload resolution only if std::is_const_v<T> is false.
The <, <=, >, >=, and != operators are synthesized from operator<=> and operator== respectively.
Contents |
Parameters
| lhs, rhs | - | reference_wrapper object to compare
|
| ref | - | reference to compare to the reference_wrapper object
|
Return value
1,2) lhs.get() == rhs.get().
3) lhs.get() == ref.
4,5) synth-three-way(lhs.get(), rhs.get()).
6) synth-three-way(lhs.get(), ref).
Exceptions
Throws when and what the comparison throws.
Example
| This section is incomplete Reason: no example |
