On May 5, 10:57 pm, Ozgur Akgun
Let me try to understand you then. What happens when you run the following command in ghci?
sample (arbitrary :: Gen (Maybe Int, Maybe Int) )
Do you still always get (Just _, Just _) or (Nothing, Nothing) pairs, or do you also get some (Nothing, Just _) or (Just _, Nothing) pairs?
Well, I couldn't run the above code, as "sample" isn't part of quickcheck-1.2. But this made me wonder whether it's a version issue. This seems to be the case. If I run this with quickcheck 2.1:
import Test.QuickCheck
main = quickCheckWith stdArgs{maxSuccess=100000} f
f :: (Maybe Int,Maybe Int) -> Bool f (Just _,Just _) = True f (Nothing,Nothing) = True f _ = False
I see a failure almost instantly. This is what I want... I don't expect all of the generated pairs to have the same constructor in each field. However, running this with quickcheck 1.2:
import Test.QuickCheck
main = quickCheckWith stdArgs{maxSuccess=100000} f
f :: (Maybe Int,Maybe Int) -> Bool f (Just _,Just _) = True f (Nothing,Nothing) = True f _ = False
I see no failures... all of the generatd pairs have the same constructor in each field. So the good news is that quickcheck 2.1 behaves as I expected. I'm still curious as to the behaviour of the older version. Tim