[Haskell-beginners] Randomly selecting a data constructor

[Thomas Davie]

data FigType = TR1 | TR2 | TR3 | TR4 | SQ | L1 | L2 | Z1 | Z2 | Z3 | Z4 | NoFigure
               deriving (Enum)

randomFigure :: IO FigType
randomFigure = toEnum <$> randomRIO (1,11)

Bob

On 14 Mar 2010, at 10:57, Evgenij Merenkov wrote:

> Hello.
> 
> I have the following data and it's constructors:
> 
> FigType = TR1 | TR2 | TR3 | TR4 | SQ | L1 | L2 | Z1 | Z2 | Z3 | Z4 | NoFigure
> 
> I need to randomly return one of them in a function. The obvious solution to me, is simply using a random number generator and case statement, where each value generated is associated with each data constructor. Like this:
> 
> import System.Random
> 
> randomFigType :: IO FigType
> randomFigure = do
>   x <- randomRIO (1::Int,11::Int)
>   return $ case x of
>              1 -> TR1
>              2 -> TR2
>              3 -> TR3
> e t.c.
> 
> But is there a more direct way to do this?
> 
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