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From: ken-w@is.s.u-tokyo.ac.jp (WAKITA Ken)
Newsgroups: comp.lang.scheme
Subject: Re: trace in xscheme
Message-ID: <1520@malta.is.s.u-tokyo.ac.jp>
Date: 30 Oct 90 09:07:12 GMT
References: <28787@boulder.Colorado.EDU>
Sender: news@is.s.u-tokyo.ac.jp
Reply-To: ken-w@is.s.u-tokyo.ac.jp
Distribution: comp
Organization: Dept. of Information Science, the Univ. of Tokyo, Japan.
Lines: 86
In-reply-to: grunwald@foobar.colorado.edu's message of 27 Oct 90 12:56:05 JST


In article <28787@boulder.Colorado.EDU> grunwald@foobar.colorado.edu (Dirk Grunwald) writes:

 > From: grunwald@foobar.colorado.edu (Dirk Grunwald)
 > Newsgroups: comp.lang.scheme
 > Date: 27 Oct 90 12:56:05 JST
 > Sender: news@boulder.Colorado.EDU
 > Reply-To: grunwald@foobar.colorado.edu
 > Distribution: comp
 > Organization: University of Colorado at Boulder
 > Lines: 205
 > 
 > 
 > I'm using xscheme-0.22 for a class in programming languages.  There's
 > no trace facility, so I wrote one. I'm wondering if anyone has written
 > any other debugging facilities; my students are having a tough time
 > with debugging xscheme programs.

     ELK does not provide trace facility.  So, I've also written
similar, shorter, but a bit dangerous program.  Though it contains
several known bugs (it can't trace macros and primitive procedures) it
is useful.  I also have written a toplevel eval-read-print loop to
support transcript-on/off facility.  An interested reader can request
via E-mail to:

        ken-w@is.s.u-tokyo.ac.jp

----------------------------------------------------------------------
(define trace)
(define untrace)

(let ()
  (define trace-list '(()))

  (define (reset-trace) (set! trace-list '(())))

  (define-macro (the-trace func)
    `(let ((the-func (eval ,func))
	   (result #v))
       (if (assoc ',func ,trace-list)
	   (error 'trace "~s already trace on." ,func))
       (if (not (compound? ,func))
	   (error 'trace "wrong argument type ~s (expected compound)"
		  (type ,func)))
       (set! ,trace-list
	     (cons ()
		   (cons (cons ',func the-func)
			 (cdr ,trace-list))))
       (set! ,func
	     (lambda param-list
	       (format #t "# Entering ~s~%"
		       (cons ',func param-list))
	       (set! result (apply the-func param-list))
	       (format #t "# Exiting  ~s ==> ~s~%"
		       (cons ',func param-list)
		       result)
	       result))))
  (print (type the-trace))

  (define-macro (the-untrace func)
    `(let ((the-func (assoc ',func ,trace-list)))
     
       (define (remove! func)
	 (let ((prev ,trace-list)
	       (here (cdr ,trace-list)))
	   (while (and here
		       (not (eq? func (caar here))))
		  (set! prev here)
		  (set! here (cdr here)))
	   (if (not here)
	       (error 'remove "item ~s not found." func)
	       (set-cdr! prev (cdr here)))))
     
       (if the-func
	   (begin (remove! ',func)
		  (set! ,func (cdr the-func))))))
  (print (type the-untrace))
  
  (set! trace the-trace)
  (set! untrace the-untrace))
----------------------------------------------------------------------

--
WAKITA Ken (ken-w@is.s.u-tokyo.ac.jp)		      Masuda Group.,
						Dept. of Info. Sci.,
						     Univ. of Tokyo.