29 Numerics library [numerics]

29.8 Generalized numeric operations [numeric.ops]

29.8.4 Inner product [inner.product]

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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);
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Requires: T shall meet the requirements of CopyConstructible (Table 24) and CopyAssignable (Table 26) types.
In the ranges [first1, last1] and [first2, first2 + (last1 - first1)] binary_­op1 and binary_­op2 shall neither modify elements nor invalidate iterators or subranges.283
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Effects: Computes its result by initializing the accumulator acc with the initial value init and then modifying it with acc = acc + (*i1) * (*i2) or acc = binary_­op1(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.
283)
The use of fully closed ranges is intentional.