defining own arbitrary :: Gen Int
Hello, I would like to define my own arbitrary which should only give naturals, i. e. which should behave like instance Arbitrary Integer where arbitrary = elements ([0..]). This definition gives a "multiple definition" error. Is there a way to hide the definition of arbitrary::Gen Int of QuickCheck, such that I can use my own definition ? Thanks a lot in advance, ben
On 7 Mar 2009, at 13:54, ben wrote:
Hello,
I would like to define my own arbitrary which should only give naturals, i. e. which should behave like
instance Arbitrary Integer where arbitrary = elements ([0..]).
This definition gives a "multiple definition" error. Is there a way to hide the definition of arbitrary::Gen Int of QuickCheck, such that I can use my own definition ?
The easiest way is to newtype it, and use fromIntegral to convert: newtype Natural = N Integer instance Arbitrary Integer where arbitrary = N <$> elements [0..] instance Integral Natural where fromIntegral (N x) = fromIntegral x Bob
participants (2)
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ben -
Thomas Davie