Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!ucsd!ucbvax!husc6!husc2!carlton
From: carlton@husc2.HARVARD.EDU (david carlton)
Newsgroups: comp.lang.scheme
Subject: frivolous Scheme things (Fun Only posting)
Message-ID: <3135@husc6.harvard.edu>
Date: 5 Jun 90 18:10:07 GMT
Sender: news@husc6.harvard.edu
Reply-To: huttar@occs.cs.oberlin.edu (Lars Huttar)
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Organization: Oberlin College CS   Oberlin, OH
Lines: 46

Here are a couple of neat little Scheme things I've come across or come
up with here at school.  I hope this is not out of line for the newsgroup,
which seems to be pretty serious.

;; #1
;; By Carl Muckenhoupt
;; Put in more lambdas if you want.
(define list (lambda lambda lambda))

;; #2   Self-rep
;; This expression prints itself out.
((lambda (s) `(,s ',s))
 '(lambda (s) `(,s ',s)))

;; #2b  Self-rep II
;; So does this one.  Which part of this one can be changed to
;; any old quoted expression?
((lambda (s t) `(,s ',s ',t))
 '(lambda (s t) `(,s ',s ',t))
 '(lambda (s t) `(,s ',s ',t)))

;; #3  Self-rep III (two-stage)
((lambda (s t) `(,s ',s ,(not t)))
 '(lambda (s t) `(,s ',s ,(not t)))
 t)

;; #3b  Self-rep IV (n-stage)
((lambda (s t) `(,s ',s ,(mod (1+ t) n)))
 '(lambda (s t) `(,s ',s ,(mod (1+ t) n)))
 0)

;; #4  call/cc nightmare (true by definition?)
(define I (lambda (x) x))
((call/cc call/cc) I)
;; What does this return, and why?
;; How about
((call/cc call/cc) (call/cc call/cc))

If you have any tidbits like these, or improvements or variations on
these, I would *love* to see them, and would be grateful if you would
send them to me.

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;;  Lars Huttar   huttar@occs.cs.oberlin.edu   Oberlin College CS
;;  US mail:      206 Merribrook Trail   Duncanville, TX  75116