instance declaration troubles
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"?