[Haskell-cafe] Custom QuickCheck Gens without custom shrinks

[Niklas Hambüchen]

Oh, this is silly. Of course it is:

   forAllShrink linesGen shrink ...

On 15/08/12 20:35, Niklas Hambüchen wrote:
> I wrote this Gen to generate lines of texts without \NUL and \n:
> 
>     fullLinesProp = forAll linesGen ...
> 
>     linesGen = listOf . listOf $ arbitrary `suchThat` (`notElem`
> ['\NUL', '\n'])
>     -- alternatively:
>     linesGen = arbitrary `suchThat` (all (all (`notElem` ['\NUL', '\n'])))
> 
> However, I just realized that QuickCheck disables shrinking when I use
> this instead of (linesGen = arbitrary :: Gen [String]).
> 
> Why is that? Is there a way to get what I want + shrinking without
> defining a custom shrink (e.g. forAllShrink)?
> 
> Thanks