vector<double>::iterator iterA = A.begin();
vector<int>::const_iterator iterB = B.begin();
vector<double>::const_iterator iterC = C.begin();
while (iterA != A.end())
  {
    *iterA += -*iterB + 2 * *iterC;
    ++iterA; ++iterB; ++iterC;
  }

Example 1: Efficient evaluation of A += -B + 2 * C.