16 Language support library [language.support]

16.11 Comparisons [cmp]

template<class T> constexpr strong_ordering strong_order(const T& a, const T& b);

Effects: Compares two values and produces a result of type strong_ordering:

(1.1)
If numeric_limits<T>::is_iec559 is true, returns a result of type strong_ordering that is consistent with the totalOrder operation as specified in ISO/IEC/IEEE 60559.
(1.2)
Otherwise, returns a <=> b if that expression is well-formed and convertible to strong_ordering.
(1.3)
Otherwise, if the expression a <=> b is well-formed, then the function is defined as deleted.
(1.4)
Otherwise, if the expressions a == b and a < b are each well-formed and convertible to bool, then
- (1.4.1)
  if a == b is true, returns strong_ordering::equal;
- (1.4.2)
  otherwise, if a < b is true, returns strong_ordering::less;
- (1.4.3)
  otherwise, returns strong_ordering::greater.
(1.5)
Otherwise, the function is defined as deleted.

template<class T> constexpr weak_ordering weak_order(const T& a, const T& b);

Effects: Compares two values and produces a result of type weak_ordering:

(2.1)
Returns a <=> b if that expression is well-formed and convertible to weak_ordering.
(2.2)
Otherwise, if the expression a <=> b is well-formed, then the function is defined as deleted.
(2.3)
Otherwise, if the expressions a == b and a < b are each well-formed and convertible to bool, then
- (2.3.1)
  if a == b is true, returns weak_ordering::equivalent;
- (2.3.2)
  otherwise, if a < b is true, returns weak_ordering::less;
- (2.3.3)
  otherwise, returns weak_ordering::greater.
(2.4)
Otherwise, the function is defined as deleted.

template<class T> constexpr partial_ordering partial_order(const T& a, const T& b);

Effects: Compares two values and produces a result of type partial_ordering:

(3.1)
Returns a <=> b if that expression is well-formed and convertible to partial_ordering.
(3.2)
Otherwise, if the expression a <=> b is well-formed, then the function is defined as deleted.
(3.3)
Otherwise, if the expressions a == b and a < b are each well-formed and convertible to bool, then
- (3.3.1)
  if a == b is true, returns partial_ordering::equivalent;
- (3.3.2)
  otherwise, if a < b is true, returns partial_ordering::less;
- (3.3.3)
  otherwise, returns partial_ordering::greater.
(3.4)
Otherwise, the function is defined as deleted.

template<class T> constexpr strong_equality strong_equal(const T& a, const T& b);

Effects: Compares two values and produces a result of type strong_equality:

(4.1)
Returns a <=> b if that expression is well-formed and convertible to strong_equality.
(4.2)
Otherwise, if the expression a <=> b is well-formed, then the function is defined as deleted.
(4.3)
Otherwise, if the expression a == b is well-formed and convertible to bool, then
- (4.3.1)
  if a == b is true, returns strong_equality::equal;
- (4.3.2)
  otherwise, returns strong_equality::nonequal.
(4.4)
Otherwise, the function is defined as deleted.

template<class T> constexpr weak_equality weak_equal(const T& a, const T& b);

Effects: Compares two values and produces a result of type weak_equality:

(5.1)
Returns a <=> b if that expression is well-formed and convertible to weak_equality.
(5.2)
Otherwise, if the expression a <=> b is well-formed, then the function is defined as deleted.
(5.3)
Otherwise, if the expression a == b is well-formed and convertible to bool, then
- (5.3.1)
  if a == b is true, returns weak_equality::equivalent;
- (5.3.2)
  otherwise, returns weak_equality::nonequivalent.
(5.4)
Otherwise, the function is defined as deleted.