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From: Tomtom <tomtom@herbesfolles.org>
Newsgroups: gmane.lisp.guile.user
Subject: manipulating continuations
Date: Sat, 12 Feb 2011 09:35:06 +0100
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Hello list

First of all, I'm new to scheme and guile - started using them a few
days ago for a project. So here we go: this is the bit of code that
causing me troubles:


(define (foo)
  (call/cc
   (lambda (return)
     (display "first part")
     (newline)
     (call/cc
      (lambda (cont)
	(return cont)))
     (display "second part")
     (newline))))



Basically, I use call/cc to stop the procedure foo after printing "first
part" and return a continuation. Then, if I call this continuation it
prints "second part" and ends. To test this code, I did this:

guile> (define c (foo))
first part
guile> (c)
second part

yay, it works. But now, what if I want to run the continuation directly,
rather than storing it and calling it later ? This is what I get:

guile> ((foo))
first part
second part

Backtrace:
In current input:
  15: 0* [#<unspecified>]

<unnamed port>:15:1: In expression ((foo)):
<unnamed port>:15:1: Wrong type to apply: #<unspecified>
ABORT: (misc-error)

There. I don't understand why I get this error message.

Cheers

Tom