help with Lisp

This problem involves arithmetic expressions, which may or may not be numbered. You may need to use the following help functions in addition to the buit-in functions including eval which evaluates an arithmetic expression. For example, (eval ‘(+ 1 2)) returns 3.

   (define (atom? x) (not (list? x))) 
(define build-aexp  
(lambda (op sub1 sub2) 
(cons op (cons sub1 (cons sub2 '()))))) 

(define numbered?  (lambda (aexp)   
(cond      
((atom? aexp) (number? aexp))      
(else (and (numbered? (cadr aexp))                 
(numbered? (caddr aexp)))))))

a)Write a function simplify which evaluates as much of an arithmetic expression as possible. For example,

(simplify '(* 2 (+ (* a (+ 3 5)) (+ 1 4)))) should return (* 2 (+ (* a 5)) b)Write a function remove-noops which eliminates any additions of 0 or multiplications by 1. For example, both

(remove-noops '(* 3 (* 1 (+ a 0)))) and (remove-noops (simplify '(* 3 (* 1 (+ a (- 1 1)))))) should return (* 3 a).

Thank you for your help

Ah, Scheme. Very fun. Are you taking SICP?

Yes scheme issue, I don't know what does SICP stand for, but it's for compiler's course, can you help me with this problem ??

SCIP = Structure and Interpretation of Computer programs.

( http://mitpress.mit.edu/sicp/full-text/book/book.html )

Compiler course? School or something like the Digital Mars Compiler weekend seminar thing? I'm not a CS. I'm self taught. Ive taken the SCIP course when MIT put it up on the Free courseware section and read a lot of books on programing but...

Its been a long time since ive done scheme and or taken that course. I know we touched on that in one of the chapters...but the only help i would be able to offer you help now a days would be general and or broad in nature (academic if you would) on this kinda problem. Well, do you need actual code or just theory?

BTW, you found a site which has users that use AutoLisp. AL is Scheme like but not really. AL is based upon a language called XLisp which was like a striped down version of Common lisp.

This would be a translation from Scheme to Autolisp so you can see the different syntax's.

Scheme:

(define (atom? x) 
 (not (list? x)) )

AutoLisp:

(defun atom? ( x / )
 (not (eq (type x) 'LIST)) )

Of course this is a direct translation and there are other ways of doing this same task in AutoLisp but you get the idea.

I would recommend that you find a newsgroup for Scheme instead of here because I think I may be the only one who has taken a Scheme class.

I gotta run now so good luck and i hope to talk to you later.