4.0 KiB
[exclusive.scan]
26 Algorithms library [algorithms]
26.10 Generalized numeric operations [numeric.ops]
26.10.8 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(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: O(last - first) 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 ith input element from the ith sum.
If binary_op is not mathematically associative, the behavior of exclusive_scan can be nondeterministic.
â end note]