std::lexicographical_compare_three_way

 

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Defined in header <algorithm>
template< class InputIt1, class InputIt2, class Cmp > constexpr auto lexicographical_compare_three_way( InputIt1 first1, InputIt1 last1,                                                   InputIt2 first2, InputIt2 last2,                                                   Cmp comp) -> decltype(comp(*first1, *first2));	(1)	(since C++20)
template< class InputIt1, class InputIt2 > constexpr auto lexicographical_compare_three_way( InputIt1 first1, InputIt1 last1,                                                   InputIt2 first2, InputIt2 last2);	(2)	(since C++20)

Lexicographically compares two ranges [first1, last1) and [first2, last2) using three-way comparison and produces a result of the strongest applicable comparison category type.

1) Behaves as if defined as follows:

for ( ; first1 != last1 && first2 != last2; void(++first1), void(++first2) )
    if (auto cmp = comp(*first1, *first2); cmp != 0)
        return cmp;
 
return first1 != last1 ? std::strong_ordering::greater :
       first2 != last2 ? std::strong_ordering::less :
                         std::strong_ordering::equal;

2) Behaves as if defined as follows:

return std::lexicographical_compare_three_way(
    first1, last1, first2, last2, std::compare_three_way());

Parameters

first1, last1	-	the first range of elements to examine
first2, last2	-	the second range of elements to examine
comp	-	a function object type. The behavior is undefined if its return type is not one of the three comparison category types (strong_ordering, weak_ordering, or partial_ordering)
Type requirements
- InputIt1, InputIt2 must meet the requirements of LegacyInputIterator.

Return value

A comparison category type as defined above.

See also

lexicographical_compare	returns true if one range is lexicographically less than another (function template)
compare_three_way (C++20)	function object implementing x <=> y (class)