25 Algorithms library [algorithms]

25.9 Generalized numeric operations [numeric.ops]

25.9.6 Partial sum [partial.sum]

template<class InputIterator, class OutputIterator> constexpr OutputIterator partial_sum(InputIterator first, InputIterator last, OutputIterator result); template<class InputIterator, class OutputIterator, class BinaryOperation> constexpr OutputIterator partial_sum(InputIterator first, InputIterator last, OutputIterator result, BinaryOperation binary_op);
Mandates: InputIterator's value type is constructible from *first.
The result of the expression std​::​move(acc) + *i or binary_­op(std​::​move(acc), *i) is implicitly convertible to InputIterator's value type.
acc is writable ([iterator.requirements.general]) to result.
Preconditions: In the ranges [first, last] and [result, result + (last - first)] binary_­op neither modifies elements nor invalidates iterators or subranges.240
Effects: For a non-empty range, the function creates an accumulator acc whose type is InputIterator's value type, initializes it with *first, and assigns the result to *result.
For every iterator i in [first + 1, last) in order, acc is then modified by acc = std​::​move(acc) + *i or acc = binary_­op(std​::​move(acc), *i) and the result is assigned to *(result + (i - first)).
Returns: result + (last - first).
Complexity: Exactly (last - first) - 1 applications of the binary operation.
Remarks: result may be equal to first.
The use of fully closed ranges is intentional.