25 Algorithms library [algorithms]

25.10 Generalized numeric operations [numeric.ops]

25.10.10 Transform exclusive scan [transform.exclusive.scan]

template<class InputIterator, class OutputIterator, class T,
         class BinaryOperation, class UnaryOperation>
  constexpr OutputIterator
    transform_exclusive_scan(InputIterator first, InputIterator last,
                             OutputIterator result, T init,
                             BinaryOperation binary_op, UnaryOperation unary_op);
template<class ExecutionPolicy,
         class ForwardIterator1, class ForwardIterator2, class T,
         class BinaryOperation, class UnaryOperation>
  ForwardIterator2
    transform_exclusive_scan(ExecutionPolicy&& exec,
                             ForwardIterator1 first, ForwardIterator1 last,
                             ForwardIterator2 result, T init,
                             BinaryOperation binary_op, UnaryOperation unary_op);

Mandates: All of

(1.1)
binary_op(init, init),
(1.2)
binary_op(init, unary_op(*first)), and
(1.3)
binary_op(unary_op(*first), unary_op(*first))

are convertible to T.

Preconditions:

(2.1)
T meets the Cpp17MoveConstructible (Table 28) requirements.
(2.2)
Neither unary_op nor binary_op 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, unary_op(*(first + 0)), unary_op(*(first + 1)), ..., unary_op(*(first + K - 1)))

Returns: The end of the resulting range beginning at result.

Complexity:

O (last - first)

applications each of unary_op and binary_op.

Remarks: result may be equal to first.

[Note 1:

The difference between transform_exclusive_scan and transform_inclusive_scan is that transform_exclusive_scan excludes the

i^{th}

input element from the

i^{th}

sum.

If binary_op is not mathematically associative, the behavior of transform_exclusive_scan might be nondeterministic.

transform_exclusive_scan does not apply unary_op to init.

— end note]