一、接口实现

功能：计算区间[first，second)内所有元素和_Val（初始值）的总和。

template<class _InIt,class _Ty,class _Fn2> inline_Ty _Accumulate(_InIt _First, _InIt _Last, _Ty _Val, _Fn2 _Func){	// return sum of _Val and all in [_First, _Last), using _Funcfor (; _First != _Last; ++_First)_Val = _Func(_Val, *_First);return (_Val);}template<class _InIt,class _Ty,class _Fn2> inline_Ty accumulate(_InIt _First, _InIt _Last, _Ty _Val, _Fn2 _Func){	// return sum of _Val and all in [_First, _Last), using _Func_DEBUG_RANGE(_First, _Last);_DEBUG_POINTER(_Func);return (_Accumulate(_Unchecked(_First), _Unchecked(_Last), _Val, _Func));}// TEMPLATE FUNCTION accumulate
template<class _InIt,class _Ty> inline_Ty accumulate(_InIt _First, _InIt _Last, _Ty _Val){	// return sum of _Val and all in [_First, _Last)return (_STD accumulate(_First, _Last, _Val, plus<>()));}

二、使用

#include <numeric>
#include <vector>
#include <iostream>using namespace std;int main(int argc, char* argv[])
{vector<int> vecs{1, 2, 3, 4, 5, 6};cout << accumulate(vecs.begin(), vecs.end(), 0) << endl;cout << accumulate(vecs.begin(), vecs.end(), 0, minus<int>()) << endl;return 0;
}

result: