How the yin-yang puzzle works?

Posted by Hrundik on Stack Overflow See other posts from Stack Overflow or by Hrundik
Published on 2010-04-22T21:32:38Z Indexed on 2010/04/23 20:33 UTC
Read the original article Hit count: 1110

Filed under:

Scheme

|

callcc

I'm trying to grasp the semantics of call/cc in Scheme, and the Wikipedia page on continuations shows the yin-yang puzzle as an example:

(let* ((yin
         ((lambda (cc) (display #\@) cc) (call-with-current-continuation (lambda (c) c))))
       (yang
         ((lambda (cc) (display #\*) cc) (call-with-current-continuation (lambda (c) c)))) )
    (yin yang))

It should output @\*@\**@\**\*@\**\**@..., but I don't understand why; I'd expect it to output @\*@\**\**\**\**\*...

Can somebody explain in detail why the yin-yang puzzle works the way it works?

© Stack Overflow or respective owner

Related posts about Scheme

About "If.." in Scheme (plt-scheme)

as seen on Stack Overflow - Search for 'Stack Overflow'
I had a pretty simple requirement in my Scheme program to execute more than one statement, in the true condition of a 'if'. . So I write my code, something like this: (if (= 1 1) ((expression1) (expression2)) ; these 2 expressions are to be executed when the condition is true (expression3)… >>> More
Detecting EOF in a Binary File using Scheme

as seen on Stack Overflow - Search for 'Stack Overflow'
(define (read-all-input) (local ((define line (bytes->list (read-bytes 4)))) (if (eof-object? line) empty (cons line (read-all-input))))) (void (read-all-input)) The above code fails because bytes-list expects an argument of type byte string, but is given # >>> More
Scheme: Detecting duplicate elements in a list

as seen on Stack Overflow - Search for 'Stack Overflow'
Does R6RS or Chez Scheme v7.9.4 have a library function to check if a list contains duplicate elements? Alternatively, do either have any built in functionality for sets (which dis-allow duplicate elements)? So far, I've only been able to find an example here. The problem with that is that it doesn't… >>> More
Traversing Scheme function as a list

as seen on Stack Overflow - Search for 'Stack Overflow'
Isn't it possible to treat functions in Scheme as any other list? Basically, what I want do to is something like this: (define (foo) "hello") (cdr foo) ; or similar, should return the list ((foo) "hello") I've found a similar discussion about this, and I feel a bit disappointed if this is not… >>> More
Scheme implementations - what does it mean?

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, I'm a beginning student in CS, and my classes are mostly in Java. I'm currently going through "Little Schemer" as a self study, and in the process of finding out how to do that I have found numerous references to "implementations" of Scheme. My question is, what are implementations? Are they… >>> More

Related posts about callcc

How does this callcc example work?

as seen on Stack Overflow - Search for 'Stack Overflow'
(callcc (fun k -> k 7)) + 3 (callcc (fun k -> 7)) + 3 What do each of these evaluate to and why? >>> More
How the yin-yang puzzle works?

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm trying to grasp the semantics of call/cc in Scheme, and the Wikipedia page on continuations shows the yin-yang puzzle as an example: (let* ((yin ((lambda (cc) (display #\@) cc) (call-with-current-continuation (lambda (c) c)))) (yang ((lambda (cc) (display #\*) cc) (call-with-current-continuation… >>> More
call/cc in Lua - Possible?

as seen on Stack Overflow - Search for 'Stack Overflow'
The Wikipedia article on Continuation says: "In any language which supports closures, it is possible to write programs in continuation passing style and manually implement call/cc." Either that is true and I need to know how to do it or it is not true and that statement needs to be corrected. If this… >>> More
Continuation (call/cc) in Scheme

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi All, I need to understand Continuations in Scheme for my upcoming exams and I have no idea about continuations at all. Can anyone please suggest me sources of how to go about learning continuations? Regards, darkie >>> More
Can continuations be used as a replacement for recursion?

as seen on Stack Overflow - Search for 'Stack Overflow'
The following function generates a 'stack level too deep (SystemStackError)' for n = 5,000 def factorial(n) n == 0 ? 1 : factorial(n -1) * n end Is there a way to avoid this error using continuations/callcc? Note: I know this can be implemented without recursion. e.g. def factorial2(n) … >>> More