泛型算法系列25:inner_product()

#include <numeric> #include <vector> #include <iostream> using namespace std; /************************************************************************/ /* */ /************************************************************************/ template<class _InIt1, class _InIt2, class _Ty> inline _Ty my_Inner_product(_InIt1 _First1, _InIt1 _Last1, _InIt2 _First2, _Ty _Val) { // return inner product of sequences _DEBUG_RANGE(_First1, _Last1); for (; _First1 != _Last1; ++_First1, ++_First2) _Val = _Val + *_First1 * *_First2; return (_Val); } /************************************************************************/ /* */ /************************************************************************/ template<class _InIt1, class _InIt2, class _Ty, class _Fn21, class _Fn22> inline _Ty my_Inner_product(_InIt1 _First1, _InIt1 _Last1, _InIt2 _First2, _Ty _Val, _Fn21 _Func1, _Fn22 _Func2) { // return inner product of sequences, using _Func1 and _Func2 _DEBUG_RANGE(_First1, _Last1); _DEBUG_POINTER(_Func1); _DEBUG_POINTER(_Func2); for (; _First1 != _Last1; ++_First1, ++_First2) _Val = _Func1(_Val, _Func2(*_First1, *_First2)); return (_Val); } int main() { int ia[] = { 2, 3, 5, 8 }; int ia2[] = { 1, 2, 3, 4 }; // multiply the element pair from the two arrays // then add to the initial value: 0 int res = my_Inner_product( &ia[0], &ia[4], &ia2[0], 0); // generates: inner product of arrays: 55 cout << "inner product of arrays: " << res << endl; vector<int> vec( ia, ia + 4 ); vector<int> vec2( ia2, ia2 + 4 ); // add the element pair from the two vectors // then subtract from the initial value: 0 res = my_Inner_product( vec.begin(), vec.end(), vec2.begin(), 0, minus<int>(), plus<int>() ); // generates: inner product of vectors: -28 cout<<"inner product of vectors: " << res << endl; return 0; }