129 lines
4.8 KiB
Markdown
129 lines
4.8 KiB
Markdown
[adjacent.difference]
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# 26 Algorithms library [[algorithms]](./#algorithms)
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## 26.10 Generalized numeric operations [[numeric.ops]](numeric.ops#adjacent.difference)
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### 26.10.12 Adjacent difference [adjacent.difference]
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[ð](#lib:adjacent_difference)
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`template<class InputIterator, class OutputIterator>
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constexpr OutputIterator
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adjacent_difference(InputIterator first, InputIterator last,
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OutputIterator result);
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template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2>
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ForwardIterator2
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adjacent_difference(ExecutionPolicy&& exec,
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ForwardIterator1 first, ForwardIterator1 last, ForwardIterator2 result);
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template<class InputIterator, class OutputIterator, class BinaryOperation>
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constexpr OutputIterator
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adjacent_difference(InputIterator first, InputIterator last,
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OutputIterator result, BinaryOperation binary_op);
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template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
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class BinaryOperation>
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ForwardIterator2
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adjacent_difference(ExecutionPolicy&& exec,
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ForwardIterator1 first, ForwardIterator1 last,
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ForwardIterator2 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#L13139)
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Let T be the value type of decltype(first)[.](#1.sentence-1)
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For the overloads that do not take an argument binary_op,
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let binary_op be an lvalue
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that denotes an object of type minus<>[.](#1.sentence-2)
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[2](#2)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L13145)
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*Mandates*:
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- [(2.1)](#2.1)
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For the overloads with no ExecutionPolicy, T is constructible from *first[.](#2.1.sentence-1)
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acc (defined below) is
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writable ([[iterator.requirements.general]](iterator.requirements.general "24.3.1 General"))
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to the result output iterator[.](#2.1.sentence-2)
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The result of the expression binary_op(val, std::move(acc)) is writable to result[.](#2.1.sentence-3)
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- [(2.2)](#2.2)
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For the overloads with an ExecutionPolicy,
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the result of the expressions binary_op(*first, *first) and *first are writable to result[.](#2.2.sentence-1)
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[3](#3)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L13162)
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*Preconditions*:
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- [(3.1)](#3.1)
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For the overloads with no ExecutionPolicy, T meets the [*Cpp17MoveAssignable*](utility.arg.requirements#:Cpp17MoveAssignable "16.4.4.2 Template argument requirements [utility.arg.requirements]") (Table [33](utility.arg.requirements#tab:cpp17.moveassignable "Table 33: Cpp17MoveAssignable requirements"))
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requirements[.](#3.1.sentence-1)
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- [(3.2)](#3.2)
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For all overloads, in the ranges [first, last]
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and [result, result + (last - first)], binary_op neither modifies elements
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nor invalidates iterators or subranges[.](#3.2.sentence-1)[209](#footnote-209 "The use of fully closed ranges is intentional.")
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[4](#4)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L13179)
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*Effects*: For the overloads with no ExecutionPolicy and a non-empty range,
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the function creates an accumulator acc of type T,
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initializes it with *first,
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and assigns the result to *result[.](#4.sentence-1)
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For every iterator i in [first + 1, last) in order,
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creates an object val whose type is T,
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initializes it with *i,
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computes binary_op(val, std::move(acc)),
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assigns the result to *(result + (i - first)), and
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move assigns from val to acc[.](#4.sentence-2)
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[5](#5)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L13192)
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For the overloads with an ExecutionPolicy and a non-empty range,
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performs *result = *first[.](#5.sentence-1)
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Then, for every d in [1, last - first - 1],
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performs *(result + d) = binary_op(*(first + d), *(first + (d - 1)))[.](#5.sentence-2)
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[6](#6)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L13198)
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*Returns*: result + (last - first)[.](#6.sentence-1)
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[7](#7)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L13202)
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*Complexity*: Exactly (last - first) - 1 applications of the binary operation[.](#7.sentence-1)
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[8](#8)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L13206)
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*Remarks*: For the overloads with no ExecutionPolicy,result may be equal to first[.](#8.sentence-1)
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For the overloads with an ExecutionPolicy,
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the ranges [first, last) and [result, result + (last - first))
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shall not overlap[.](#8.sentence-2)
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[209)](#footnote-209)[209)](#footnoteref-209)
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The use of fully closed ranges is intentional[.](#footnote-209.sentence-1)
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