How about this? class ArbitraryDefault a where {} instance (Integral a, Bounded a, ArbitraryDefault a) => Arbitrary a where arbitrary = arbitraryBound coarbitrary a = error "Not implemented" instance ArbitraryDefault Word16 instance ArbitraryDefault Word32 instance ArbitraryDefault Word64 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) Joel Reymont wrote:
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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