[Haskell-cafe] Polymorphic QuickCheck arguments

Dougal Stanton dougal at dougalstanton.net
Tue Jun 17 06:05:01 EDT 2008

2008/6/17 Hugo Pacheco <hpacheco at gmail.com>:
> Hi all,
> There is something about polymorphic tests in QuickCheck that I do not
> understand.
> If you write the simplest dummy test function
> tst :: a -> Bool
> tst _ = True
> and evaluate it we get
>> verboseCheck tst
> 0:
> ()
> 1:
> ()
> ...
> How come did the polymorphic value a get instanciated to ()? Is this done
> via the Testable type class?

I haven't got something here to check with, but from the formatting it
looks like every odd line is a randomly-chosen boolean value, and the
following line is the result? It might be just printing the result
value of IO (). Maybe try a more complete test to see how that looks?



Dougal Stanton
dougal at dougalstanton.net // http://www.dougalstanton.net

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