On Mon, Dec 29, 2008 at 6:24 PM,
Are there anyway to express the "iterating" of a user-defined data type in Haskell?
For example, in
data Shape = Square | Circle | Triangle
how can I 'iterate' them and apply them all to the same function without indicating them explicitly? such as [func Square, func Circle, func Triangle]. Can I use a form similar to the following case in a list instead:
Numbers = [1,2,3,4,5]
[func x | x <- Numbers ]
Actually what I want is to obtain all the possible values of a data type (Shape).
For "enum" style data, where all the constructors have no arguments, you can do deriving (Bounded, Enum), so: data Shape = Square | Circle | Triangle deriving (Bounded,Enum) Then: numbers = [minBound..maxBound] :: [Shape] Luke