A question on a piece of code written using call/cc

A question on a piece of code written using call/cc

[Yi DAI]

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Hi,


I recently test a piece of code written using call/cc on Guile and several
other Scheme implementations, but get different results. The code piece is
as follows:

(let ((n 0)
      (c (call/cc (lambda (k) k))))
  (display n)
  (newline)
  (set! n (+ n 1))
  (c c))

What I wanna do is try to print out the sequence of natural numbers using
call/cc. On Guile, it works well. But other implementations (Chicken,
Bigloo, Racket) all print out (an infinite sequence of) 0. I am puzzled. Any
idea?


-- 
DAY

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Re: A question on a piece of code written using call/cc

[Andy Wingo]

Hi Yi,

On Tue 31 Aug 2010 21:10, Yi DAI <plm.day@gmail.com> writes:

> (let ((n 0) 
>       (c (call/cc (lambda (k) k))))
>   (display n)
>   (newline)
>   (set! n (+ n 1))
>   (c c))
>
> What I wanna do is try to print out the sequence of natural numbers
> using call/cc. On Guile, it works well. But other implementations
> (Chicken, Bigloo, Racket) all print out (an infinite sequence of) 0. I
> am puzzled. Any idea?

Guile from master returns a sequence of zeros as well. I'm not sure why
older Guile behaves differently.

I think in any case for your program to be correct, you need to use let*
instead of let.

Andy
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