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cppdraft/exclusive/scan.md

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+[exclusive.scan]
+
+# 26 Algorithms library [[algorithms]](./#algorithms)
+
+## 26.10 Generalized numeric operations [[numeric.ops]](numeric.ops#exclusive.scan)
+
+### 26.10.8 Exclusive scan [exclusive.scan]
+
+[🔗](#lib:exclusive_scan)
+
+`template<class InputIterator, class OutputIterator, class T>
+  constexpr OutputIterator
+    exclusive_scan(InputIterator first, InputIterator last,
+                   OutputIterator result, T init);
+`
+
+[1](#1)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L12710)
+
+*Effects*: Equivalent to:return exclusive_scan(first, last, result, init, plus<>());
+
+[🔗](#lib:exclusive_scan_)
+
+`template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class T>
+  ForwardIterator2
+    exclusive_scan(ExecutionPolicy&& exec,
+                   ForwardIterator1 first, ForwardIterator1 last,
+                   ForwardIterator2 result, T init);
+`
+
+[2](#2)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L12728)
+
+*Effects*: Equivalent to:return exclusive_scan(std::forward<ExecutionPolicy>(exec),
+ first, last, result, init, plus<>());
+
+[🔗](#lib:exclusive_scan__)
+
+`template<class InputIterator, class OutputIterator, class T, class BinaryOperation>
+  constexpr OutputIterator
+    exclusive_scan(InputIterator first, InputIterator last,
+                   OutputIterator result, T init, BinaryOperation binary_op);
+template<class ExecutionPolicy,
+         class ForwardIterator1, class ForwardIterator2, class T, class BinaryOperation>
+  ForwardIterator2
+    exclusive_scan(ExecutionPolicy&& exec,
+                   ForwardIterator1 first, ForwardIterator1 last,
+                   ForwardIterator2 result, T init, BinaryOperation binary_op);
+`
+
+[3](#3)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L12752)
+
+*Mandates*: All of 
+
+- [(3.1)](#3.1)
+
+binary_op(init, init),
+
+- [(3.2)](#3.2)
+
+binary_op(init, *first), and
+
+- [(3.3)](#3.3)
+
+binary_op(*first, *first)
+
+are convertible to T[.](#3.sentence-1)
+
+[4](#4)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L12763)
+
+*Preconditions*: 
+
+- [(4.1)](#4.1)
+
+  T meets the [*Cpp17MoveConstructible*](utility.arg.requirements#:Cpp17MoveConstructible "16.4.4.2 Template argument requirements [utility.arg.requirements]") (Table [31](utility.arg.requirements#tab:cpp17.moveconstructible "Table 31: Cpp17MoveConstructible requirements")) requirements[.](#4.1.sentence-1)
+
+- [(4.2)](#4.2)
+
+  binary_op neither invalidates iterators or subranges,
+ nor modifies elements in
+ the ranges [first, last] or [result, result + (last - first)][.](#4.2.sentence-1)
+
+[5](#5)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L12774)
+
+*Effects*: For each integer K in [0, last - first)
+assigns through result + K the value of:*GENERALIZED_NONCOMMUTATIVE_SUM*( binary_op, init, *(first + 0), *(first + 1), …, *(first + K - 1))
+
+[6](#6)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L12783)
+
+*Returns*: The end of the resulting range beginning at result[.](#6.sentence-1)
+
+[7](#7)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L12787)
+
+*Complexity*: O(last - first) applications of binary_op[.](#7.sentence-1)
+
+[8](#8)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L12791)
+
+*Remarks*: result may be equal to first[.](#8.sentence-1)
+
+[9](#9)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L12795)
+
+[*Note [1](#note-1)*:
+
+The difference between exclusive_scan and inclusive_scan is
+that exclusive_scan excludes the ith input element
+from the ith sum[.](#9.sentence-1)
+
+If binary_op is not mathematically associative,
+the behavior of exclusive_scan can be nondeterministic[.](#9.sentence-2)
+
+— *end note*]