Is it possible to generate a list from a datatype's possible values in Haskell? [duplicate]

Question

Can a list be generated from a type's possible values? E.g.

data Shape = Circle | Rectangle | Triangle | Pentagon

to

[Circle,Rectangle,Triangle,Pentagon]

Answer 1

Yes it can. It's a duty of Enum and Bounded type classes e.g.

λ data Shape = Circle | Rectangle | Triangle | Pentagon deriving (Show, Enum, Bounded)
λ [minBound .. maxBound] :: [Shape]
[Circle,Rectangle,Triangle,Pentagon]
λ [minBound ..] :: [Shape]
[Circle,Rectangle,Triangle,Pentagon]