2008/2/10, Michael Feathers
How bad is this:
addProduct :: [Product] -> Product -> [Product] addProduct inventory product = nub (product : inventory)
This is pretty terrible, if the list is consumed afterward (which we assume it will be) we should have something like a O(n^3) complexity... Since nub is O(n^2).
compared to this:
addProduct :: [Product] -> Product -> [Product] addProduct inventory p | isNothing (find (==p) inventory) = p : inventory | otherwise = inventory
This is much better, though probably better writed :
addProduct :: [Product] -> Product -> [Product] addProduct inventory p | elem p inventory = p : inventory | otherwise = inventory
and probably even better with a Set instead of a List... -- Jedaï