Re: Re[2]: overlapping instances and constraints

On 2/28/06, Claus Reinke <claus.reinke@talk21.com> wrote:

I'm not sure what you're talking about? both hugs and ghc clearly specify that the more specific instance declaration is chosen when overlapping instance declarations are permitted.

I have trouble with this "more specific" term. It's not well-defined, i.e. not a total order on possible instance declarations. The point I was trying to make was that in the case where a precondition (in this case, Fail a) does not apply, what stops the resolution algorithm falling back on the other instance declaration? -- Taral <taralx@gmail.com> "Computer science is no more about computers than astronomy is about telescopes." -- Edsger Dijkstra