From Newsgroup: comp.lang.lisp

If a list contains repeated elements they should be replaced
with a single copy of the element. The order of the elements
should not be changed.

Example:
* (compress '(a a a a b c c a a d e e e e))
(A B C A D E)

Gauche Scheme

Assuming that the list doesn't contain #f.

(define (del-dups seq)
(fold-right*
(lambda (e f accum) (if (equal? e f) accum (cons e accum)))
'()
seq))

(del-dups '(a a a a b c c a a d e e e e))
===>
(a b c a d e)

Given:

(define (fold-right* kons knil xs)
(fold-right
(lambda (e accum)
(kons e (if (pair? accum) (car accum) #f) accum))
knil
xs))
--
[T]he problem is that lispniks are as cultish as any other devout group and basically fall down frothing at the mouth if they see [heterodoxy].
--- Kenny Tilton
The good news is, it's not Lisp that sucks, but Common Lisp. --- Paul Graham --- Synchronet 3.21a-Linux NewsLink 1.2