[Haskell-cafe] QuickCheck behaving strange

[Felipe Lessa]

On Fri, Jul 24, 2009 at 08:11:12PM +0200, Tobias Olausson wrote:
> prop_schedule :: Ord t => [Interval a t] -> Bool
> prop_schedule []        = True
> prop_schedule [a]       = True
> prop_schedule (x:y:ys)  = end x <= begin y && prop_schedule (y:ys)
[..]
> How come QuickCheck passes 100 tests of random lists? One would think that
> at least one of the generated lists would be unsorted. It also passes
> 1000 and even
> 10000 tests.

Probably it was defaulting to 'Interval () ()'.  Try to do

   :s -Wall

on your GHCi prompt to see when these things happen.

--
Felipe.