On Thu, Aug 16, 2001 at 01:11:25AM -0400, Avi Pfeffer wrote:
> Works fine. Things get tricky when I try to add pairs. In order to type
> a pair expression, I find I need to create a Pair class and introduce a
> class constraint:
>
> class Pair a b c | a -> b c, b c -> a
>
> instance Pair (b,c
How about:
===
data Expr a = Haskell a
| If (Expr Bool) (Expr a) (Expr a)
| forall b . Appl (Expr (b->a)) (Expr b)
| forall b c . MkPair (Expr b) (Expr c) (b -> c -> a)
eval :: Expr a -> a
eval (
Hi all,
I'm trying to write an interpreter for a language embedded in Haskell,
that "inherits" Haskell types and values. So I create a type Expr a, to
represent expressions of type a, and an evaluator that takes an Expr a
and produces an a. (To keep things simple, let's assume there are no
vari
