[Haskell-beginners] quickCheck generation question

Joe Van Dyk joe at fixieconsulting.com
Sat Oct 8 07:08:32 CEST 2011


Solved this:  http://stackoverflow.com/questions/7693930/generating-a-lists-of-a-specific-length-with-haskells-quickcheck

On Fri, Oct 7, 2011 at 4:40 PM, Joe Van Dyk <joe at fixieconsulting.com> wrote:
> I'm going through the 99 Haskell problems and am trying to write
> quickCheck properties for each one.
>
> -- 3 (find k"th element of a list)
> element_at xs x = xs !! x
> prop_3a xs x = (x < length xs && x >= 0) ==> element_at xs (x::Int) ==
> (xs !! x::Int)
>
> When I run prop_3a through quickCheck, it gives up, saying that it
> only passed 1 test.  This makes sense, because the random x is going
> to be larger than the number of elements in the random list in most
> cases.
>
> So what I need to do is write a generator that generates a random list
> with length larger than a random integer, but I'm not sure how to do
> that.
>
> Thanks!
> Joe
>



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