GNU bug report logs - #14537
defect in guile with syntax transformation

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: ludo <at> gnu.org (Ludovic Courtès)
Cc: tracker <at> debbugs.gnu.org
Subject: bug#14537: closed (defect in guile with syntax transformation)
Date: Mon, 03 Jun 2013 22:41:02 +0000

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Your message dated Tue, 04 Jun 2013 00:38:44 +0200
with message-id <87zjv6ddl7.fsf <at> gnu.org>
and subject line Re: bug#14537: defect in guile with syntax transformation
has caused the debbugs.gnu.org bug report #14537,
regarding defect in guile with syntax transformation
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


-- 
14537: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=14537
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Contact help-debbugs <at> gnu.org with problems

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From: "Dr. M. Luedde" <mirko_luedde <at> yahoo.de>
To: bug-guile <at> gnu.org
Cc: mirko.luedde <at> sap.com
Subject: defect in guile with syntax transformation
Date: Sun, 2 Jun 2013 09:14:48 +0100 (BST)

;; I think the below code exhibits a defect with guile 1.8.7.
;;
;; The `defrec' syntax transformer (defined below) does not behave
;; correctly within an imbedding `let' expression.
;;
;; The system is CYGWIN_NT-6.1-WOW64 WDFN00305859A 1.7.18(0.263/5/3)
;; 2013-04-19 10:39 i686 Cygwin
;;
;; Guile runs in GNU bash, version 4.1.10(4)-release (i686-pc-cygwin)

;; enable `define-syntax' functionality
(use-modules (ice-9 syncase))
;; OK

(let ( (n 99) )
  (begin
    (define
      ev.OK? (lambda (x) (if (zero? x) #t
			     (od.OK? (- x 1)))))
    (define
      od.OK? (lambda (x) (if (zero? x) #f
			     (ev.OK? (- x 1))))))
  (od.OK? 99))
;; OK, evaluates to #t

(define-syntax defrec
  ;; TYPE: syntax transformer.
  ;;
  ;; REQUIRES: (defrec . X) requires that X := ((S_1 V_1) ... (S_N
  ;; V_N)). The S_I are mutually distinct symbols. The V_J may contain
  ;; references to the S_I. On evaluation of any V_J the value bound
  ;; to a referenced S_I must not be needed.
  ;;
  ;; RETURNS: The value of the expression (begin (define S_1 #f)
  ;; ... (define S_N #f) (set! S_1 V_1) ... (set! S_N V_N)).
  (syntax-rules ()
    ((_ (S V) ...)
     (begin (define S #f) ...
	    (set! S V) ...))))
;; OK

(defrec
  (ev.broken? (lambda (x) (if (zero? x) #t
			      (od.broken? (- x 1)))))
  (od.broken? (lambda (x) (if (zero? x) #f
			      (ev.broken? (- x 1))))))
(od.broken? 99)
;; OK, evaluates to #t

(let ( (n 99) )
  (defrec
    (ev.broken? (lambda (x) (if (zero? x) #t
				(od.broken? (- x 1)))))
    (od.broken? (lambda (x) (if (zero? x) #f
				(ev.broken? (- x 1))))))
  (od.broken? n))
;; Produces an error message: 
;; In standard input:
;;   14: 0* (let* ((n 99)) (defrec (ev.broken? #) (od.broken? #)) (od.broken? n))

;; standard input:14:1: In procedure memoization in expression (let* (#) (defrec # #) ...):
;; standard input:14:1: In file "standard input", line 14: Mixed definitions and expressions in (defrec (ev.broken? (lambda (x) (if (zero? x) #t (od.broken? (- x 1))))) (od.broken? (lambda (x) (if (zero? x) #f (ev.broken? (- x 1)))))).
;; Backtrace:
;; ABORT: (syntax-error)
--
Dr. M. Luedde, Rheinblick 26A, D-69226 Nussloch, Germany
+49-175-2779708, Skype: MirkoLuedde

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From: ludo <at> gnu.org (Ludovic Courtès)
To: "Dr. M. Luedde" <mirko_luedde <at> yahoo.de>
Cc: "14537 <at> debbugs.gnu.org" <14537-done <at> debbugs.gnu.org>,
	"mirko.luedde <at> sap.com" <mirko.luedde <at> sap.com>
Subject: Re: bug#14537: defect in guile with syntax transformation
Date: Tue, 04 Jun 2013 00:38:44 +0200

Hello,

"Dr. M. Luedde" <mirko_luedde <at> yahoo.de> skribis:

> alright, I compiled guile 2.0.6 on my cygwin system. 
>  
> Given the amount and content of the warnings, it came as a surprise to me that the compilation apparently was successul and the resulting guile did process my testcase without the previously exhibited errors.
>  
> I consider this defect report closed. 

OK, thanks!

I know my answer may have sounded a bit frustrating, but it’s been more
than two years since 2.0 was released.  It’s really a huge step forward
compared to Guile 1.8, and we hope people can appreciate it and find it
a good incentive to upgrade.

Ludo’.

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