instance declaration troubles

Nick Name
Fri, 7 Mar 2003 17:02:16 +0100

On Fri, 7 Mar 2003 07:47:09 -0800 (PST)
Hal Daume III <hdaume@ISI.EDU> wrote:

>  That said, "undecidable instances" sound very scary, but they're
>  really not.  You can google around for a conversation I had with SPJ
>  about this a while back, but something being an und instance is a
>  compile time property.  That is, if compilation succeeds, you don't
>  have anything to worry about and the worst that can happen at
>  compilation time is that you'll hit the bottom of this stack.

Thanks, you've been clear, even I miss that in haskell98 one can't
define subset properties between type classes... maybe because that
would mean "subtyping"?