Init

cppdraft/alg/three/way.md

@@ -0,0 +1,58 @@
+[alg.three.way]
+
+# 26 Algorithms library [[algorithms]](./#algorithms)
+
+## 26.8 Sorting and related operations [[alg.sorting]](alg.sorting#alg.three.way)
+
+### 26.8.12 Three-way comparison algorithms [alg.three.way]
+
+[🔗](#lib:lexicographical_compare_three_way)
+
+`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](#1)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L11857)
+
+Let N be min(e1 - b1, e2 - b2)[.](#1.sentence-1)
+
+Let E(n) be comp(*(b1 + n), *(b2 + n))[.](#1.sentence-2)
+
+[2](#2)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L11861)
+
+*Mandates*: decltype(comp(*b1, *b2)) is a comparison category type[.](#2.sentence-1)
+
+[3](#3)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L11865)
+
+*Returns*: E(i), where i is the smallest integer in [0, N)
+such that E(i) != 0 is true, or(e1 - b1) <=> (e2 - b2) if no such integer exists[.](#3.sentence-1)
+
+[4](#4)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L11871)
+
+*Complexity*: At most N applications of comp[.](#4.sentence-1)
+
+[🔗](#lib:lexicographical_compare_three_way_)
+
+`template<class InputIterator1, class InputIterator2>
+  constexpr auto
+    lexicographical_compare_three_way(InputIterator1 b1, InputIterator1 e1,
+                                      InputIterator2 b2, InputIterator2 e2);
+`
+
+[5](#5)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L11885)
+
+*Effects*: Equivalent to:return lexicographical_compare_three_way(b1, e1, b2, e2, compare_three_way());