[Haskell-cafe] Quickcheck examples and Data.Word32

[Joel Reymont]

I came up with this but can it be done better? I'm wishing for  
"default class methods" :-).

instance Arbitrary Word16 where
     arbitrary = arbitraryBound
     coarbitrary a = error "Not implemented"

instance Arbitrary Word32 where
     arbitrary = arbitraryBound
     coarbitrary a = error "Not implemented"

instance Arbitrary Word64 where
     arbitrary = arbitraryBound
     coarbitrary a = error "Not implemented"

arbitraryBound :: forall a.(Integral a, Bounded a) => Gen a
arbitraryBound = do let mx,mn :: Integer
                         mx = fromIntegral (maxBound :: a)
                         mn = fromIntegral (minBound :: a)
                     c <- choose (mx, mn)
                     return (fromIntegral c)

On Oct 27, 2005, at 6:13 PM, Joel Reymont wrote:

> Is there a way to squeeze this boilerplate code?
>
> class Arbitrary
> instance Arbitrary Word16 where
>     arbitrary = do let mx,mn :: Integer
>                        mx = fromIntegral (maxBound :: Word16)
>                        mn = fromIntegral (minBound :: Word16)
>                    c <- choose (mx, mn)
>                    return (fromIntegral c)
>     coarbitrary a = error "Not implemented"
>
> instance Arbitrary Word32 where
>     arbitrary = do let mx,mn :: Integer
>                        mx = fromIntegral (maxBound :: Word32)
>                        mn = fromIntegral (minBound :: Word32)
>                    c <- choose (mx, mn)
>                    return (fromIntegral c)
>     coarbitrary a = error "Not implemented"
>
> instance Arbitrary Word64 where
>     arbitrary = do let mx,mn :: Integer
>                        mx = fromIntegral (maxBound :: Word64)
>                        mn = fromIntegral (minBound :: Word64)
>                    c <- choose (mx, mn)
>                    return (fromIntegral c)
>     coarbitrary a = error "Not implemented"
>

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