[Haskell-cafe] HTF & Quickcheck

[graham at fatlazycat.com]

Thanks, how does using /= not cause test failures ? Just the sample rate
will be high enough ?

On Tue, Dec 18, 2012, at 06:04 PM, Simon Hengel wrote:
> On Tue, Dec 18, 2012 at 05:25:41PM +0000, graham at fatlazycat.com wrote:
> > Are there any libraries that define various common generators ?
> > 
> > What would be the cleanest way to define two positive integers below
> > 1000 that are different ? Seems relatively easy with conditionals.
> 
> You can still use (==>) to ensure that two numbers are different.  I
> would use something like this:
> 
>     newtype Small = Small Int
>       deriving Show
> 
>     instance Arbitrary Small where
>       arbitrary = Small . (`mod` 1000) <$> arbitrary
> 
>     prop_foo (Small x) (Small y) = x /= y ==> ...
> 
> Cheers,
> Simon