[racket] how does call/cc and let/ec exactly works?

[김태윤]

hello 

I am thinking of such a code like..

#lang scheme

(require racket/gui)

(let ([v (let/ec out

               (dynamic-wind

                (lambda () (display "in "))

                (lambda ()

                  (display "pre ")

                  (display (call/cc out))

                  #f)

                (lambda () (display "out "))))])

      (when v (v "post ")))

but I still have no idea how 

"in pre out in post out " is printed but not "in pre out in pre post out "

how does call/cc and let/ec exactly works?

[김태윤]

thank you for your replying

does call/cc always working with let/ec?

when it comes to compare with your code, it looks like..

call/cc is meaning of "get out of this function and evaluate next function and comeback (to inside of let/ec) for evaluate rest of the code"

is it right?

if so, I don't understand why 

following code does not working properly

#lang scheme

(require racket/gui)

(define (aa) #t #f "11")

(dynamic-wind

 (lambda () (display "in "))

 (lambda ()

   (display "pre ")

   (let/ec out

     

     (display (call/cc out)))

   (display "1")

   (display "2")

   (display "3")

   )

 (lambda () (display "out ")))

but the following code works weird

#lang scheme

(require racket/gui)

(define (aa) #t #f "11")

(dynamic-wind

 (lambda () (display "in "))

 (lambda ()

   (display "pre ")

   (let/ec out

     (display (call/cc out)))

   (display "1")

   (display "2")

   (display "3")

   "1")

 (lambda () (display "out ")))

2010년 10월 18일 오후 7:59, Jos Koot <jos....@telefonica.net>님의 말:

Compare yoiur code with:

 

#lang scheme

(require racket/gui)

(dynamic-wind
 (lambda () (display "in "))
 (lambda ()
   (display "pre ")

   (let/ec out

     (display (call/cc out)))

   #f)
 (lambda () (display "out ")))

 

Jos

---

From: users-...@racket-lang.org [mailto:users-...@racket-lang.org] On Behalf Of ???
Sent: 18 October 2010 12:41
To: us...@racket-lang.org
Subject: [racket] how does call/cc and let/ec exactly works?

[Jens Axel Søgaard]

2010/10/18 김태윤 <kty...@gmail.com>:

> how does call/cc and let/ec exactly works?

Read

http://www.cs.indiana.edu/hyplan/dfried/appcont.pdf

--
Jens Axel Søgaard
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