27 Algorithms library [algorithms]

27.10 Generalized numeric operations [numeric.ops]

27.10.8 Exclusive scan [exclusive.scan]

```template<class InputIterator, class OutputIterator, class T> constexpr OutputIterator exclusive_scan(InputIterator first, InputIterator last, OutputIterator result, T init); ```
Effects: Equivalent to: return exclusive_scan(first, last, result, init, plus<>());
```template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class T> ForwardIterator2 exclusive_scan(ExecutionPolicy&& exec, ForwardIterator1 first, ForwardIterator1 last, ForwardIterator2 result, T init); ```
Effects: Equivalent to: return exclusive_scan(std::forward<ExecutionPolicy>(exec), first, last, result, init, plus<>());
```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); ```
Mandates: All of
• binary_op(init, init),
• binary_op(init, *first), and
• binary_op(*first, *first)
are convertible to T.
Preconditions:
• T meets the Cpp17MoveConstructible (Table 31) requirements.
• binary_op neither invalidates iterators or subranges, nor modifies elements in the ranges [first, last] or [result, result + (last - first)].
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))
Returns: The end of the resulting range beginning at result.
Complexity: applications of binary_op.
Remarks: result may be equal to first.
[Note 1:
The difference between exclusive_scan and inclusive_scan is that exclusive_scan excludes the input element from the sum.
If binary_op is not mathematically associative, the behavior of exclusive_scan can be nondeterministic.
â€” end note]