Using vector from other class as reverse iterator

Question

I'm on thin ice here, Sorry. I have not used reverse iterators before, and like you can see in my code is that I also want to use a vector from another class as THE iterator object:

double indicators::sRSItemp(input* Close1, int StartDay) {
  int n = 14;
  double rs;
  double rsi;
  double tmpavl;
  double tmpavg;


if (!RSI.empty()) {
for ( vector<double>::reverse_iterator i = Close1->Close.rbegin(); i != Close1->Close.rend(); ++i ) {

    if (Close1->Close[i] < Close1->Close[(i + 1)]){
        tmpavl = ((AVL[0] * 13 ) + (Close1->Close[(i +1)] - Close1->Close[i] ) / n);
        cout << "AVLtmp " << AVL[0] << endl; 
        cout << "tmpavl " << tmpavl << endl;
        AVL.insert(AVL.begin(), tmpavl);
        cout << "AVL is " << AVL[0] << endl;

        tmpavg = ((AVG[0] * 13 ) / n );
        AVG.insert(AVG.begin(), tmpavg);
        // cout << "AVG is " << AVG[i] << endl;
        }

        else if  (Close1->Close[i] > Close1->Close[(i + 1)]) { 
            tmpavg = ((AVG[0] * 13 ) + (Close1->Close[i] - Close1->Close[(i +1)]) / n );
            AVG.insert(AVG.begin(), tmpavg);
            // cout << "AVG is " << AVG[i] << endl;

            tmpavl = ((AVL[0] * 13 ) / n );
            AVL.insert(AVL.begin(), tmpavl); 
            // cout << "AVL is " << AVL[i] << endl;

            }

            rs = AVG[0] / AVL[0];
            rsi = (100.0 - (100.0 / (1.0 + rs)));
            RSI.insert(RSI.begin(), rsi);

            }
    }
return 0;
}

But when I compile this code I get several errors like this : error: no match for ‘operator[]’ (operand types are ‘std::vector’ and ‘std::vector::reverse_iterator {aka std::reverse_iterator<__gnu_cxx::__normal_iterator > >}’), pointing to my vector indexing ??

if (Close1->Close[i] < Close1->Close[(i + 1)]){

Like I said this is new territory for me, and the fault I guess lies with the declaration of the iterator ? When I iterate through the same vector (front-to-back) in other code there are no problems. Help much appreciated!

Answer 1

The square brackets operator of std::vector accepts indexes, not iterators.

Here you're trying to use iterators as indexes:

if (Close1->Close[i] < Close1->Close[(i + 1)]) {

Instead of passing iterators to operator [], you should just use asterisks to dereference them, in order to get to vector elements they are pointing to:

if (*i < *(i + 1)) {

---

Also, be careful with dereferencing i + 1: on the last iteration of your loop i + 1 will be equal to rend() (the reverse past-the-last element iterator). Attempting to access anything via such an iterator will result in undefined behavior.