10 Jan
2008
10 Jan
'08
9:11 a.m.
On Jan 10, 2008 2:04 PM, Nicholls, Mark
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