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  int CrossOver(SCFloatArrayRef First, SCFloatArrayRef Second, int Index)
  {
    float X1 = First[Index-1];
    float X2 = First[Index];
    float Y1 = Second[Index-1];
    float Y2 = Second[Index];

    if (X2 != Y2) // The following is not useful if X2 and Y2 are equal
    {
      // Find non-equal values for prior values
      int PriorIndex = Index - 1;
      while (X1 == Y1 && PriorIndex > 0 && PriorIndex > Index - 100)
      {
        --PriorIndex;
        X1 = First[PriorIndex];
        Y1 = Second[PriorIndex];
      }
    }

    if (X1 > Y1 && X2 < Y2)
      return CROSS_FROM_TOP;
    else if (X1 < Y1 && X2 > Y2)
      return CROSS_FROM_BOTTOM;
    else
      return NO_CROSS;
  }