Someone said something about having 2 instances of the type in the typeclass.....maybe I misinterpreted it.
> -----Original Message----- > From: Luke Palmer [mailto:[EMAIL PROTECTED] > Sent: 10 January 2008 14:12 > To: Nicholls, Mark > Cc: Bulat Ziganshin; haskell-cafe@haskell.org > Subject: Re: Re[2]: [Haskell-cafe] confusion about 'instance'.... > > On Jan 10, 2008 2:04 PM, Nicholls, Mark <[EMAIL PROTECTED]> wrote: > > I can translate OO into mathematical logic pretty easily, I was trying > > to do the same thing (informally of course) with Haskell....but things > > are not quite what they appear....not because of some OO hang up (which > > I probably have many)...but because of what "type class" actually means. > > But you can think of a type class as a set of types! The problem is that > if we allow certain kinds of instances (such as the Foo instance I gave > earlier) then the set is allowed to be non-recursive (only recursively > enumerable), so determining whether a particular type is a member of it > would be undecidable. > > Luke _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
