29 Numerics library [numerics]

29.8 Generalized numeric operations [numeric.ops]

29.8.9 Transform exclusive scan [transform.exclusive.scan]

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

Requires:

(1.1)
T shall be MoveConstructible (Table 23).
(1.2)
All of
- (1.2.1)
  binary_op(init, init),
- (1.2.2)
  binary_op(init, unary_op(*first)), and
- (1.2.3)
  binary_op(unary_op(*first), unary_op(*first))
shall be convertible to T.
(1.3)
Neither unary_op nor binary_op shall invalidate iterators or subranges, or 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,
    unary_op(*(first + 0)), unary_op(*(first + 1)), ..., unary_op(*(first + K - 1)))

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

Complexity: applications each of unary_op and binary_op.

Remarks: result may be equal to first.

[ Note

The difference between transform_exclusive_scan and transform_inclusive_scan is that transform_exclusive_scan excludes the input element from the sum.

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

transform_exclusive_scan does not apply unary_op to init.

— end note

]