interface PriceCells {
  bool isCellLimit(double price);
  
  // next-higher cell limit or NaN if no more cells
  double nextCellLimit(double price);
  
  // next-lower cell limit or NaN if no more cells
  double previousCellLimit(double price);
  
  // go n steps down
  double nCellLimitsDown(double price, int n);
  
  // go n steps up
  double nCellLimitsUp(double price, int n);
  
  // convert to "cell space" (0=first cell limit, 1=next cell limit, -1=previous cell limit etc)
  double priceToCellNumber aka toCellNumber(double price);
  
  double cellNumberToPrice aka fromCellNumber(double cellNumber);
  
  default double basePrice() { ret cellNumberToPrice(0); }
}