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