need help with this cudder

Okay, I have this data structure (Haskell):
data Lisp = Nil | Atom String | Cons Lisp Lisp
I'm trying to write a function for correctly rendering the data... however, I cannot figure out how to... I have re-read SICP, but was unable to find an answer, I also re-read McCarthy's paper, which didn't help either.  This is what I have so far:
displayLisp Nil = "()" -- this doesn't matter so much, could be #nil or NIL something
displayLisp (Atom x) = x
displayLisp (Cons car cdr) = "(" ++ (displayLisp car) ++ " . " ++ (displayLisp cdr) ++ ")"
Now what to do about lists?  I know there's a list when the final cdr is NIL, but... hmm.  And also, I think you can have lists where the final element is not NIL as well (is that so?).

I can parse no problem (well, a little, I'm forced to omit the spaces around the . in the conses to avoid some ambiguity) -- lists, conses, etc.

Please help me Sussman!

read SICP.

>>2
I have re-read SICP, but was unable to find an answer

displayLisp (Cons car Nil) = ...
displayLisp (Cons car cdr@(Atom x)) = ...
displayLisp (Cons car cdr) = "(" ++ (displayLisp car) ++ " " ++ (displayLisp cdr)

... are left as an exercise for the reader.

>>2
DON'T HELP HIM

I came up with something!  If I use a different function for rendering cars and cdrs, perhaps it'll work!

This appears to pass all the test cases I have, comments?

displayLisp Nil = "NIL"
displayLisp (Atom x) = x
displayLisp (Cons car cdr) = "(" ++ (displayLisp car) ++ (displayCudder cdr)

displayCdr Nil = ")"
displayCdr (Atom x) = " . " ++ x ++ ")"
displayCdr (Cons car cdr) = " " ++ (displayLisp car) ++ (displayCudder cdr)

I feel the need, the need for weed!

Marijuana MUST be legalized.

Cons of light hope.

<-- check em dubz

13 Name: Anonymous 2012-01-04 21:14

>>11
COOL DUBZ, BRO