59 lines
1.9 KiB
Markdown
59 lines
1.9 KiB
Markdown
[alg.three.way]
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# 26 Algorithms library [[algorithms]](./#algorithms)
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## 26.8 Sorting and related operations [[alg.sorting]](alg.sorting#alg.three.way)
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### 26.8.12 Three-way comparison algorithms [alg.three.way]
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[ð](#lib:lexicographical_compare_three_way)
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`template<class InputIterator1, class InputIterator2, class Cmp>
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constexpr auto
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lexicographical_compare_three_way(InputIterator1 b1, InputIterator1 e1,
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InputIterator2 b2, InputIterator2 e2,
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Cmp comp)
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-> decltype(comp(*b1, *b2));
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`
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[1](#1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L11857)
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Let N be min(e1 - b1, e2 - b2)[.](#1.sentence-1)
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Let E(n) be comp(*(b1 + n), *(b2 + n))[.](#1.sentence-2)
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[2](#2)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L11861)
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*Mandates*: decltype(comp(*b1, *b2)) is a comparison category type[.](#2.sentence-1)
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[3](#3)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L11865)
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*Returns*: E(i), where i is the smallest integer in [0, N)
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such that E(i) != 0 is true, or(e1 - b1) <=> (e2 - b2) if no such integer exists[.](#3.sentence-1)
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[4](#4)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L11871)
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*Complexity*: At most N applications of comp[.](#4.sentence-1)
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[ð](#lib:lexicographical_compare_three_way_)
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`template<class InputIterator1, class InputIterator2>
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constexpr auto
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lexicographical_compare_three_way(InputIterator1 b1, InputIterator1 e1,
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InputIterator2 b2, InputIterator2 e2);
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`
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[5](#5)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L11885)
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*Effects*: Equivalent to:return lexicographical_compare_three_way(b1, e1, b2, e2, compare_three_way());
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