This program yeilds: Fail: toEnum{Color}: tag (4) is outside of enumeration's range (0,3) in ghc... any ideas why? -mike On Thu, Nov 21, 2002 at 10:07:12AM -0500, Dean Herington wrote:
"Mike T. Machenry" wrote:
Andrew and list,
I am a beginer. I really don't know what I would do if I derived Color from Enum. You say I could create elements that way. Is there some simple example someone could post to the list? Thank you for your help.
Here's one way to generate random values from an enumerable set:
import Random
randomR_Enum :: (Enum a, RandomGen g) => (a, a) -> g -> (a, g) randomR_Enum (lo, hi) gen = (toEnum val, gen') where (val, gen') = randomR (fromEnum lo, fromEnum hi) gen
random_EnumBounded :: (Enum a, Bounded a, RandomGen g) => g -> (a, g) random_EnumBounded = randomR_Enum (minBound, maxBound)
data Color = Blue | Red | Green deriving (Show, Enum, Bounded) instance Random Color where randomR = randomR_Enum random = random_EnumBounded
main = do stdGen <- getStdGen print (take 10 (randoms stdGen :: [Color]))
Dean