isWellFormed :: Book -> Bool
isWellFormed Book{..} = let x = reverse (map bPrice (S.toList bBuyOrders)) ++ map sPrice (S.toList bSellOrders)
  in sort x == x
isWellFormed :: Book -> Bool
isWellFormed Book{..} = let x = reverse (map bPrice (S.toList bBuyOrders)) ++ map sPrice (S.toList bSellOrders)
  in sort x == x
isWellFormed Book{..} = let x = reverse (map bPrice (S.toList bBuyOrders)) ++ map sPrice (S.toList bSellOrders)
  in sort x == x