Am 10/17/2015 um 08:08 AM schrieb Ruben Astudillo:
data Process = Train PlaceDep PlaceArr TP | MovingBelt PlaceDep PlaceArr BP deriving (Eq, Show)
data TP = TP Int deriving (Eq, Show) data BP = BP Int deriving (Eq, Show)
You could use a newtype here.
Point taken
What I don't like about this is that the fact that all Processes have PlaceDep and PlaceArr appears somewhat "coincidental".
This in contrast, captures the common parts more clearly:
type PlaceDep = Int type PlaceArr = Int
data ProcessParams = DepartureTime Int | Speed Int deriving (Eq, Show)
data Process = Process PlaceDep PlaceArr ProcessParams deriving (Eq, Show)
prc1 = Process 10 11 (DepartureTime 1) prc2 = Process 12 13 (Speed 2)
This just seems a trade-off if you want to know with what are you dealing just matching the outer constructor or more of the problem won't care about it. Not really a dichotomy worth caring about much anyways
I'll have to think about this. Wouldn't this be a problem when writing functions which operate on a Process of any type? Like e.g. changeDeparture :: PlaceDep -> Process -> Process I would have to pattern match against all the constructors, wouldn't I? If I don't have just two Processes types, but 20 of them, wouldn't that become messy? In the second approach I only have to match Process and I can be certain there is a PlaceDep to be altered.