[Haskell-cafe] Re: Is curryfication practical with dynamic scope?
loup.vaillant at gmail.com
Sun Apr 26 17:00:47 EDT 2009
Well, 2 things: first, I meant "currying". second, I found the answer: no.
Under dynamic typing, the reduction steps are:
(\a -> \b -> a) 1 2
(\b -> a) 2 -- the substitution don't occur right away (that would be
?? "a" is not in the environment!!
Sorry for the noise.
PS: In a meta interpreter, lexical scope seems to be actually easier
to implement than dynamic scope.
2009/4/26 Loup Vaillant <loup.vaillant at gmail.com>:
> Hi, can this code
> (\a -> \b -> a) 1 2
> eval to normal form in a strict language with dynamic scope?
> PS: some context:
> I am currently implementing a toy language. The AST is this one:
> data whnf = -- Weak Head Normal Form
> | Unit
> | Int of int
> | Bool of bool
> | Prim of (whnf -> whnf) -- curried
> | Fun of string * expr -- curried
> data expr =
> | Whnf of whnf
> | Var of string
> | App of expr * expr
> | If of expr * expr * expr
> Dynamic typing, dynamic scope, and, as you can see, functions have to
> be curried. I plan to implement lexical scope.
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