Re: [Haskell-cafe] model theory for type classes

2012-08-23 Thread Brent Yorgey
On Thu, Aug 23, 2012 at 01:25:39PM +0100, Patrick Browne wrote: If there is no model expansion could it be because of the constructor discipline, which only allows variables, and constructors in the LHS argument patterns. Indeed, a variable name as a pattern on the LHS of a function

Re: [Haskell-cafe] model theory for type classes

2012-08-23 Thread Patrick Browne
On 23/08/12, Brent Yorgey byor...@seas.upenn.edu wrote:fun1 returns 8 for all inputs.  The fact that fun1's definition usesthe name 'constant' which happens to have the same name as somethingin scope is irrelevant.  For example, this is precisely the same as the above:constant :: Intconstant =

Re: [Haskell-cafe] model theory for type classes

2012-08-23 Thread wren ng thornton
On 8/23/12 1:02 PM, Patrick Browne wrote: I am just not sure whether there is a model expansion from the super-class model to the subclass model. If by model expansion from... you mean that there is a canonical/unique/special mapping from every superclass model to some subclass model, then