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cppdraft/partial/sum.md

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+[partial.sum]
+
+# 26 Algorithms library [[algorithms]](./#algorithms)
+
+## 26.10 Generalized numeric operations [[numeric.ops]](numeric.ops#partial.sum)
+
+### 26.10.7 Partial sum [partial.sum]
+
+[🔗](#lib:partial_sum)
+
+`template<class InputIterator, class OutputIterator>
+  constexpr OutputIterator
+    partial_sum(InputIterator first, InputIterator last,
+                OutputIterator result);
+template<class InputIterator, class OutputIterator, class BinaryOperation>
+  constexpr OutputIterator
+    partial_sum(InputIterator first, InputIterator last,
+                OutputIterator result, BinaryOperation binary_op);
+`
+
+[1](#1)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L12657)
+
+*Mandates*: InputIterator's value type is constructible from *first[.](#1.sentence-1)
+
+The result of the
+expression std​::​move(acc) + *i or binary_op(std​::​move(acc), *i) is implicitly convertible to InputIterator's value type[.](#1.sentence-2)
+
+acc is writable ([[iterator.requirements.general]](iterator.requirements.general "24.3.1 General")) to result[.](#1.sentence-3)
+
+[2](#2)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L12665)
+
+*Preconditions*: In the ranges [first, last] and [result, result + (last - first)]binary_op neither modifies elements
+nor invalidates iterators or subranges[.](#2.sentence-1)[208](#footnote-208 "The use of fully closed ranges is intentional.")
+
+[3](#3)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L12674)
+
+*Effects*: For a non-empty range,
+the function creates an accumulator acc whose type is InputIterator's value type,
+initializes it with *first,
+and assigns the result to *result[.](#3.sentence-1)
+
+For every iterator i in [first + 1, last) in order,acc is then modified byacc = std​::​move(acc) + *i or acc = binary_op(std​::​move(acc), *i) and the result is assigned to *(result + (i - first))[.](#3.sentence-2)
+
+[4](#4)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L12686)
+
+*Returns*: result + (last - first)[.](#4.sentence-1)
+
+[5](#5)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L12690)
+
+*Complexity*: Exactly (last - first) - 1 applications of the binary operation[.](#5.sentence-1)
+
+[6](#6)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L12694)
+
+*Remarks*: result may be equal to first[.](#6.sentence-1)
+
+[208)](#footnote-208)[208)](#footnoteref-208)
+
+The use of fully closed ranges is intentional[.](#footnote-208.sentence-1)