Re: [Haskell-cafe] Quickcheck examples and Data.Word32

27 Oct 2005


      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"
--
http://wagerlabs.com/