Lab4: substitution in Haskell

[Marcus Hedenström]

Hi,
We have translated our definitions to lambda abstractions, an are able to look them up from evalExp (Application expression).

f a b c = a + b +c
main = f 1 2 4

Fetch lambda abstraction:
\a -> \b -> \c -> a + b + c

Abstraction type: EAbstraction Exp Exp
substitute :: Exp -> Value -> Exp
substitute abstraction value = ??????????

How would we know (or the interpreter, rather) which variables among all variables in the lambda abstraction are to be replaced?

Thanks!
- Marcus

[Arnar Birgisson]

Hi,

On Mon, Mar 8, 2010 at 21:45, Marcus Hedenström
<marcus.h...@gmail.com> wrote:
> Abstraction type: EAbstraction Exp Exp
> substitute :: Exp -> Value -> Exp
> substitute abstraction value = ??????????
>
> How would we know (or the interpreter, rather) which variables among all variables in the lambda abstraction are to be replaced?

First of all you should reconsider your EAbstraction grammar rule.
Does it really make sense for the first part to be an arbitrary
expression? E.g. is \(x+y) -> y a valid abstraction?

Having fixed that, I think the answer to your original question will
become clear. :)

cheers,
Arnar