std::lexicographical_compare_3way (3) Linux Manual Page

std::lexicographical_compare_3way – std::lexicographical_compare_3way

Synopsis

Defined in header <algorithm>

template< class InputIt1, class InputIt2, class Cmp >

constexpr auto lexicographical_compare_3way( InputIt1 first1, InputIt1 last1,

InputIt2 first2, InputIt2 last2,                                                              (1) (since C++20)

Cmp comp)

-> std::common_comparison_category_t<decltype(comp(*first1, *first2)), std::strong_ordering>;

template< class InputIt1, class InputIt2 >

constexpr auto lexicographical_compare_3way( InputIt1 first1, InputIt1 last1,                 (2) (since C++20)

InputIt2 first2, InputIt2 last2);

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_3way(first1, last1, first2, last2,
                                         [](const auto &t, const auto &u) {
                                             return std::compare_3way(t, u);
                                         });

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 five comparison category types (strong_equality, weak_equality, 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.

Example

 This section is incomplete
 Reason: no example

See also

compare_3way compares two values using three-way comparison
             (function template)
(C++20)