# 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
• binary_­op(init, init),
• binary_­op(init, unary_­op(*first)), and
• binary_­op(unary_­op(*first), unary_­op(*first))
are convertible to T.
Preconditions:
• T meets the Cpp17MoveConstructible (Table 28) requirements.
• 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: 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 input element from the sum.
If binary_­op is not mathematically associative, the behavior of transform_­exclusive_­scan can be nondeterministic.
transform_­exclusive_­scan does not apply unary_­op to init.
— end note]