29 Numerics library [numerics]

29.8 Generalized numeric operations [numeric.ops]

29.8.7 Exclusive scan [exclusive.scan]

template<class InputIterator, class OutputIterator, class T> 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> 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);

Requires:

  • T shall be MoveConstructible (Table 23).

  • All of binary_­op(init, init), binary_­op(init, *first), and binary_­op(*first, *first) shall be convertible to T.

  • binary_­op shall neither invalidate iterators or subranges, nor modify 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 ith input element from the ith sum. If binary_­op is not mathematically associative, the behavior of exclusive_­scan may be nondeterministic. end note]