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

data Shape = Circle | Rectangle | Triangle | Pentagon

to

[Circle,Rectangle,Triangle,Pentagon]

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  • Yep it's a duplicate. This question should be closed. Commented Aug 14, 2013 at 13:01

1 Answer 1

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20

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]
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