[Haskell-cafe] QuickCheck Arbitrary - infinite recursion on recursive GADTs?

[Bryan O'Sullivan]

Marc Weber wrote:

> data A = A INt
>        | B [A]
> 
> instace Arbitrary A where
>   arbitrary = oneof [ liftM A arbitrary
>                     , liftM B arbitrary
>                     ]
> 
> But now QuickCheck will propably create a test value
> A ( B [ A ( B [ A .... -> no end
> 
> Is there an easy QuickCheck way to prevent this?

There are two successive sections in the QuickCheck manual that cover 
exactly this topic.

http://www.cs.chalmers.se/~rjmh/QuickCheck/manual_body.html#15

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