[Ineke]

I'm currently meant to be implementing the Lambda Calculus in the functional programming language, LISP

I will probably have lost most people in the above sentence, but for anyone that just knows LISP i just need help with some stupid brackets that are appearing where they shouldnt be!

this is my current code

(defun variable? (term) (if (eq (car term) 'VAR) t (if (eq (car term) 'var) t ())))
(defun abstraction? (term) (if (eq (car term) 'LAMBDA) t (if (eq (car term) 'lambda) t ())))
(defun application? (term) (if (eq (car term) 'APP) t (if (eq (car term) 'app) t ())))

(defun var-symbol (term) (if (variable? term) (cdr term) ()))
(defun make-var (term) (cons 'VAR (list term)))

(defun abs-var (term) (if (abstraction? term) (cadr term) ()))
(defun abs-body (term) (if (abstraction? term) (cddr term) ()))
(defun make-abs (term1 term2) (cons 'LAMBDA (cons term1 (list term2))))

(defun app-fn (term) (if (application? term) (car term) ()))
(defun app-arg (term) (if (application? term) (cdr term) ()))
(defun make-app (term1 term2) (cons 'APP (cons term1 (list term2))))

and we've been told that typing in

(make-abs 'x (make-app (make-var 'x) (make-var 'x)))

should return

(LAMBDA x (APP (VAR x) (VAR x)))

which it does! but then we were told that applying abs-body to it should return

(APP (VAR x) (VAR x))

but i get

((APP (VAR x) (VAR x)))

any ideas?!

[Man2u2uk]

Damn that confused me

[Ineke]

it has aparantly been joked that LISP stands for "let's insert some parentheses" ...they're not wrong!
I don't know what it actually stands for!

[Catalyst]

I don't know LISP and while I'd usually drift off to learn some at this point I've got too much work

So all I can suggest is that you might try this free IDE for LISP that I found via Google http://student.agh.e...ualclisp/en.htm

It might at least help with syntax errors, like missing brackets

[Telos]

Hmm... I'm imagining 2000 lines of that and how clear it looks then Sorry I can't help you with your problem, don't know nothing about LISP.

[Karl Buckland]

I'm sorry that I don't know any lisp... or actually I'm not because it looks a bit nasty.

Can you lay out each statement on multiple lines, or does lisp insist on having each statement on it's own line? Laying out the statements on multiple lines might take up more room but it'll be easier to read, and with indentation with the parenthesis you'll be able to see where you've missed one more easily?

I had similiar hell at Uni with Haskell and Prolog, so I can sympathise. At least Lisp is (I think) more well known than those, so you might be able to find some help on the net.

[benbacardi]

Sirkent, on Nov 29 2007, 10:20 AM, said:

I had similiar hell at Uni with Haskell and Prolog

<hijack>I used to like Prolog!</hijack>

[Ineke]

i got up the courage to ask my lecturer, who has managed to fix that little glitch, however i have a lot more of the program to write
is there anyone who knows lisp here, as in if i have any other issues is there any point me posting here or not?

[Ben Abrams]

Ineke, on Nov 30 2007, 11:28 AM, said:

i got up the courage to ask my lecturer, who has managed to fix that little glitch, however i have a lot more of the program to write
is there anyone who knows lisp here, as in if i have any other issues is there any point me posting here or not?

want to post the answer and answer the thread?

[Ineke]

yea why not, basicaly, in the line with the abs-body it needs to be caddr not cddr near the end as this prevents it from being returned as a list!

[EncoderDecoder]

what's lisp..? this is my first time hearing about this..