your quick check property (in a different way of writing) is the following:
prop_1 :: Maybe Double -> Bool prop_1 v = v == v but what you want is actually the following: prop_2 :: Maybe Double -> Maybe Double -> Bool prop_2 v1 v2 = v2 == v2 if I understood the problem correctly, using prop_2 should solve it. just run verboseCheck<http://hackage.haskell.org/packages/archive/QuickCheck/1.1.0.0/doc/html/Test-QuickCheck.html#v:verboseCheck>on these two and observe the results. Best, On 5 May 2010 08:47, Tim Docker <t...@dockerz.net> wrote: > I've notice a behaviour of quickcheck that is unexpected to me. With > this code: > > import Test.QuickCheck > > main = check myconfig > ((\v -> v == v) :: (Maybe Double,Maybe Double) -> Bool) > > myconfig = defaultConfig{configMaxTest=100000, > configEvery = \n args -> show n ++ ":\n" > ++ unlines args} > > I am relying on the default Arbitrary instances to generate pairs of > maybe doubles. But to my surprise, all of the pairs have these patterns: > > (Just _ Just _) > (Nothing, Nothing) > > I never see patterns: > > (Just _, Nothing) > (Nothing, Just _) > > Why is this the case? > > Thanks, > > Tim > > > > > > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > -- Ozgur Akgun
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