[partial.sum]

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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.200

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)).

Remarks: result may be equal to first.

200)200)

The use of fully closed ranges is intentional.

26 Algorithms library [algorithms]

26.10 Generalized numeric operations [numeric.ops]

26.10.7 Partial sum [partial.sum]