[Haskell-cafe] Re: The Proliferation of List-Like Types

On 2008-02-20, John Goerzen wrote:

I notice that Data.Foldable does some similar things but does not use multi-parameter type classes. I seem to recall that I attempted to do this in the same manner, but got tripped up somewhere. I can't remember now exactly what the problem was, but I can go back and look if nobody knows off-hand.

I went back and looked. The problem is that ByteString doesn't work as a member of Foldable, or of ListLike without it being MPTC. Trying to do so yields: ListLike.hs:217:20: Kind mis-match Expected kind `* -> *', but `BS.ByteString' has kind `*' In the instance declaration for `F.Foldable BS.ByteString' Is there any way around that, other than MPTC? -- John