Summing struct members inside a vector

Question

Consider the following:

typedef struct {
    int a;
    int b;
    int c;
    int d;
} ABCD;

typedef std::vector VecABCD;

Say

Answer 1

Another option would be to use pointer-to-members:

int CalcSumOf(const VecABCD & vec, int ABCD::*member)
{
    int sum = 0;
    for(VecABCD::const_iterator it = vec.begin(), end = vec.end(); it != end; ++it)
        sum += (*it).*member;
    return sum;
}
...
int sumA = CalcSumOf(myVec, &ABCD::a);  // find sum of .a members
int sumB = CalcSumOf(myVec, &ABCD::b);  // find sum of .b members
// etc.