25 Algorithms library [algorithms]

25.8 Sorting and related operations [alg.sorting]

25.8.11 Three-way comparison algorithms [alg.three.way]

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template<class InputIterator1, class InputIterator2, class Cmp> constexpr auto lexicographical_compare_three_way(InputIterator1 b1, InputIterator1 e1, InputIterator2 b2, InputIterator2 e2, Cmp comp) -> decltype(comp(*b1, *b2));
1
#
Mandates: decltype(comp(*b1, *b2)) is a comparison category type.
2
#
Effects: Lexicographically compares two ranges and produces a result of the strongest applicable comparison category type.
Equivalent to: 
for ( ; b1 != e1 && b2 != e2; void(++b1), void(++b2) )
  if (auto cmp = comp(*b1,*b2); cmp != 0)
    return cmp;
return b1 != e1 ? strong_ordering::greater :
       b2 != e2 ? strong_ordering::less :
                  strong_ordering::equal;
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template<class InputIterator1, class InputIterator2> constexpr auto lexicographical_compare_three_way(InputIterator1 b1, InputIterator1 e1, InputIterator2 b2, InputIterator2 e2);
3
#
Effects: Equivalent to: 
return lexicographical_compare_three_way(b1, e1, b2, e2, compare_three_way());