std::strong_order

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Defined in header <compare>
template< class T > constexpr std::strong_ordering strong_order(const T& a, const T& b);		(since C++20)

Compares two values using 3-way comparison and produces a result of type std::strong_ordering

Specifically,

• First, if std::numeric_limits<T>::is_iec559 is true, performs the ISO/IEC/IEEE 60559 totalOrder comparison of floating-point values and returns that result as a value of type std::strong_ordering (note: this comparison can distinguish between the positive and negative zero and between the NaNs with different representations)
• Otherwise, if the expression a <=> b is well-formed and its result is convertible to std::strong_ordering, returns that result.
• Otherwise, if the expression a <=> b is well-formed, but its result is not convertible to std::strong_ordering, then the function is defined as deleted.
• Otherwise, if the expression a <=> b is ill-formed, but the expressions a == b and a < b are both well-formed and convertible to bool,

• if a == b is true, returns std::strong_ordering::equal
• otherwise, if a < b is true, returns std::strong_ordering::less
• otherwise, returns std::strong_ordering::greater

• Otherwise, the function is defined as deleted.

Parameters

a, b

-

values to compare

Return value

A value of type std::strong_ordering, as described above.

See also

strong_ordering (C++20)	the result type of 3-way comparison that supports all 6 operators and is substitutable (class)
weak_order (C++20)	performs 3-way comparison and produces a result of type std::weak_ordering (function template)