[inner.product]

# 26 Algorithms library [[algorithms]](./#algorithms)

## 26.10 Generalized numeric operations [[numeric.ops]](numeric.ops#inner.product)

### 26.10.5 Inner product [inner.product]

[🔗](#lib:inner_product)

`template<class InputIterator1, class InputIterator2, class T>
  constexpr T inner_product(InputIterator1 first1, InputIterator1 last1,
                            InputIterator2 first2, T init);
template<class InputIterator1, class InputIterator2, class T,
         class BinaryOperation1, class BinaryOperation2>
  constexpr T inner_product(InputIterator1 first1, InputIterator1 last1,
                            InputIterator2 first2, T init,
                            BinaryOperation1 binary_op1,
                            BinaryOperation2 binary_op2);
`

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L12469)

*Preconditions*: T meets
the [*Cpp17CopyConstructible*](utility.arg.requirements#:Cpp17CopyConstructible "16.4.4.2 Template argument requirements [utility.arg.requirements]") (Table [32](utility.arg.requirements#tab:cpp17.copyconstructible "Table 32: Cpp17CopyConstructible requirements (in addition to Cpp17MoveConstructible)"))
and [*Cpp17CopyAssignable*](utility.arg.requirements#:Cpp17CopyAssignable "16.4.4.2 Template argument requirements [utility.arg.requirements]") (Table [34](utility.arg.requirements#tab:cpp17.copyassignable "Table 34: Cpp17CopyAssignable requirements (in addition to Cpp17MoveAssignable)")) requirements[.](#1.sentence-1)

In the ranges [first1, last1] and
[first2, first2 + (last1 - first1)]binary_op1 and binary_op2 neither modifies elements nor invalidates iterators or subranges[.](#1.sentence-2)[207](#footnote-207 "The use of fully closed ranges is intentional.")

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L12482)

*Effects*: Computes its result by
initializing the accumulator acc with the initial value init and then modifying it withacc = std​::​move(acc) + (*i1) * (*i2) oracc = 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[.](#2.sentence-1)

[207)](#footnote-207)[207)](#footnoteref-207)

The use of fully closed ranges is intentional[.](#footnote-207.sentence-1)