Why can't for_each modify its functor argument?

http://www.cplusplus.com/reference/algorithm/for_each/ Unary function taking an element in the range as argument. This can either be a pointer to a function or an object whose class overloads operator(). Its return value, if any, is ignored. According to this article, I expected that for_each actually modifies the object given as its third argument, but it seems like for_each operates on a temporary object, and doesn't even modify the object given to it. So, why is it implemented in that way? It seems much less useful. Or did I misunderstand something and my code below contains errors? ``` #include <iostream> #include <vector> #include <algorithm> template <class T> struct Multiplicator{ T mresult; public: const T& result() const{return mresult;} Multiplicator(T init_result = 1){ mresult = init_result; } void operator()(T element){ mresult *= element; std::cout << element << " "; // debug print } }; int main() { std::vector<double> vec; vec.push_back(1); vec.push_back(2); vec.push_back(3); Multiplicator<double> multiply; std::for_each(vec.begin(),vec.end(),multiply); std::cout << "\nResult: " << multiply.result() << std::endl; return 0; } ``` Expected output: ``` 1 2 3 Result: 6 ``` But got following output: ``` 1 2 3 Result: 1 ```