[Haskell-cafe] Using Quick Check generators for getting arbitrary value streams

Anton Nikishaev me
Thu Oct 10 19:12:22 UTC 2013

Luke Evans <luke at eversosoft.com> writes:

> I was hoping I could use Arbitrary instances to generate streams of
> values for test data.  It looks like you're not 'supposed' to be
> trying this, other than for the specific purpose of then testing some
> properties on these streams within Quick Check itself.
> I'm looking for something like the sample' function in Quick Check,
> only to produce an infinite stream of values (rather than the 11
> values that are clearly designed simply to give you a sense of the
> output of a generator).
> Am I out of luck, or is there yet some cunning way of doing this
> without hacking the Quick Check package to export the MkGen
> constructor?

You can make a generator that itself produces infinite list. There's
ready-made function in Test.QuickCheck.Instances.List for that (package


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