25 Algorithms library [algorithms]

25.9 Generalized numeric operations [numeric.ops]

25.9.7 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 26) 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
:
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 may be nondeterministic.
— end note
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