Trying to create simple template sum of container

[Clark]

I'm just trying to create a simple sum function template to find the sum of doubles within a container using STL. First I'm just trying to test this with a list, but I keep getting an error on line 28.

#include <iterator>
#include <list>    
#include <iostream>

using namespace std;

template <typename T>
double Sum(typename T& container)
{// sum of a container with doubles
    typename T::const_iterator iterator_begin = container.begin();
    typename T::const_iterator iterator_end = container.end();

    double my_sum = 0;

    for (iterator_begin; iterator_begin != iterator_end; iterator_begin++)
        my_sum += iterator_begin->second; // this is line 28

        return my_sum;
}

int main()
{
    list<double> test_list(10,5.1); // create a list of size 10 with values 5.1

    cout << Sum(test_list) << endl;

    return 0;
}

I get two compiler errors:

c:\users...\iterators.cpp(28): error C2839: invalid return type 'const double *' for overloaded 'operator ->'

c:\users...\iterators.cpp(28): error C2039: 'second' : is not a member of 'std::_List_const_iterator<_Mylist>'

Even if I change from const_iterator to iterator, I still receive a similar error:

error C2839: invalid return type 'double *' for overloaded 'operator ->'

Am I using the pointers wrong here or something? Thanks!

[Clark]

Error was that second is not a member of list. Rather, it's a member of map.