[Haskell-beginners] Quickcheck2 - writing a modifier for test data

[Nathan Hüsken]

That was it.
Thanks!

On 03/31/2013 12:30 PM, Brent Yorgey wrote:
> On Sun, Mar 31, 2013 at 12:21:48PM +0200, Nathan Hüsken wrote:
>>
>>      No instance for (QuickCheck-2.4.2:Test.QuickCheck.Arbitrary.Arbitrary
>>                         ValidPos)
>
> The fact that it actually lists the package and version number in the
> error message strongly suggests that the problem is conflicting
> versions of the QuickCheck package.  Do 'ghc-pkg list QuickCheck' to
> see if you have multiple versions installed, and unregister all but
> one of them.
>
> -Brent
>
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