* Stephen Tetley [2013-01-13 08:49:08+0000]

In general you can't do this whether you use pats of QuickCheck or not - `randomEvalute` would need to inspect the supplied function to see how many input parameters it has so it can list them, but there is no such introspection in Haskell.

This can be done with relatively simple type class hackery. In fact, QuickCheck already does that in order to generate arguments and print them in case of failure. Roman

I think it's more complicated because he doesn't know what the return type or arity of the function is. In QuickCheck they know the return type of a property is Bool. In this case, we only know that the return type is an instance of Show. I don't think that's enough to simply implement this. On Sunday, January 13, 2013, Stephen Tetley wrote:

Yes - I was just checking the first QuickCheck paper to see how the authors did this.

You would need a new type class that works like `Testable` and the versions of associated machinery `forAll` and `evaluate` to unroll function application.

On 13 January 2013 09:28, Roman Cheplyaka javascript:;> wrote:

...

This can be done with relatively simple type class hackery. In fact, QuickCheck already does that in order to generate arguments and print them in case of failure.

Roman

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I have a working code of this but for that I have to reimplement Arbitrary and Testable typeclasses which I don't want to do. I thought it might be possible to use parts of quickcheck without actually changing its code but still I am unable to find a suitable solution. -Satvik On Sun, Jan 13, 2013 at 2:58 PM, Roman Cheplyaka wrote:

* Stephen Tetley [2013-01-13 08:49:08+0000]

...

In general you can't do this whether you use pats of QuickCheck or not - `randomEvalute` would need to inspect the supplied function to see how many input parameters it has so it can list them, but there is no such introspection in Haskell.

This can be done with relatively simple type class hackery. In fact, QuickCheck already does that in order to generate arguments and print them in case of failure.

Roman