Calculate the inner product of the elements in two sequences

Source code

Declaration

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);

Description     For the sequence in the range [ first1, last1) , and the sequence in the range beginning at first2 , the first inner_product  function returns

, and the second inner_product  function returns

. The first function may be used to calculate the sum-of-products   of the elements in two sequence, and the second function may be used more generally to compute the inner product   of the elements of two sequences using two binary functions (these may be the same function).

If the product-of-sums   is desired, the second function may be used with a function object that returns the sum  of the contents of two iterators passed for the binary_op2 parameter and a function object that returns the product  of an object of type T and an object of the return type of binary_op2 passed for the binary_op1 parameter.

Type requirements

• InputIterator1 and InputIterator2 must be at least input iterators .
• BinaryOperation2 must be a function object type that provides T3 operator()(T1, T2), where T1 and T2 are the dereference types for InputIterator1 and InputIterator2, respectively.
• BinaryOperation1 Plus must be a function object type that provides T operator()(T, T3) .

Group Generalized numeric operations.

Time complexity Linear.

The number of applications of operator+ or the function object binary_op1, and the number of applications of operator* or the function object binary_op2, is n, where n is the size of the range [ first1, last1) , each.

Space complexity Constant.

Mutative? No.

Details Returns init if first1 = last1. Assumes that binary_op1 and binary_op2 do not cause side effects .

Glossary terms BinaryOperation, constant space, dereference type, function object, function object type, inner product, InputIterator, iterator, linear time, mutative, operator+, operator*, range, sequence, side effect.

Example Select here to view the source code for the example.

Implementation Select here to view source code (Copyright (C) 1994, Hewlett-Packard Company) for this algorithm.

Implementation notes The inner product   is calculated by adding  (or performing the first specified binary operation) the product  (or the second specified binary operation) of each pair of values, in order, to the initial value to create a modified initial value.