23 Algorithms library [algorithms]

23.9 Generalized numeric operations [numeric.ops]

23.9.3 Inner product [inner.product]

template<class InputIterator1, class InputIterator2, class T> T inner_product(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, T init); template<class InputIterator1, class InputIterator2, class T, class BinaryOperation1, class BinaryOperation2> T inner_product(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, T init, BinaryOperation1 binary_op1, BinaryOperation2 binary_op2);
Requires: T shall satisfy the Cpp17CopyConstructible (Table 26) and Cpp17CopyAssignable (Table 28) requirements.
In the ranges [first1, last1] and [first2, first2 + (last1 - first1)] binary_­op1 and binary_­op2 shall neither modify elements nor invalidate iterators or subranges.242
Effects: Computes its result by initializing the accumulator acc with the initial value init and then modifying it with acc = std::move(acc) + (*i1) * (*i2) or acc = binary_­op1(std::move(acc), binary_­op2(*i1, *i2)) for every iterator i1 in the range [first1, last1) and iterator i2 in the range [first2, first2 + (last1 - first1)) in order.
The use of fully closed ranges is intentional.