[Bug-kawa] [bugs #10561] define-syntax and case generate bad code

[Per Bothner]

This mail is an automated notification from the bugs tracker
 of the project: Kawa.

/**************************************************************************/
[bugs #10561] Latest Modifications:

Changes by: 
                Per Bothner <address@hidden>
'Date: 
                Mon 10/04/2004 at 22:16 (GMT)

            What     | Removed                   | Added
---------------------------------------------------------------------------
          Resolution | None                      | Postponed
         Assigned to | None                      | bothner


------------------ Additional Follow-up Comments ----------------------------
I haven't chased this all they way, but I'm not too surprised. The interaction 
between quote handling and hygiene is a bit kludgy.  The basic problem is that 
Kawa handles hygiene by symbol renaming, which conflicts with quote; the 
implemented solution is not very robust.

A better solution may be to implement hygiene using lexical closures.  I 
suspect syntax-case uses some variant of the latter.  I'd like to take some 
time out and clean up macro handling in Kawa, including solid 
let-syntax/letrec-syntax support, fixing quote handling, and useful (maybe 
complete) support for implementation.  I'd prefer to defer this bug until then.







/**************************************************************************/
[bugs #10561] Full Item Snapshot:

URL: <http://savannah.gnu.org/bugs/?func=detailitem&item_id=10561>
Project: Kawa
Submitted by: Chris Dean
On: Sun 10/03/2004 at 03:03

Category:  Scheme language
Severity:  5 - Average
Item Group:  Unexpected result
Resolution:  Postponed
Privacy:  Public
Assigned to:  bothner
Status:  Open


Summary:  define-syntax and case generate bad code

Original Submission:  Both (foo) and (bar) below should return the same result, 
but
(foo) returns the wrong result due to improper macro expansion.



(define-syntax log-mode
  (syntax-rules ()
    ((log-mode mode)
     (case 'mode
       ((error) "error mode")
       ((warning) "warning mode")
       (else "bad mode")))))

(define (foo)
  (log-mode warning))

(define (bar)
  (case 'warning
    ((error) "error mode")
    ((warning) "warning mode")
    (else "bad mode")))




Follow-up Comments
------------------


-------------------------------------------------------
Date: Mon 10/04/2004 at 22:16       By: Per Bothner <bothner>
I haven't chased this all they way, but I'm not too surprised. The interaction 
between quote handling and hygiene is a bit kludgy.  The basic problem is that 
Kawa handles hygiene by symbol renaming, which conflicts with quote; the 
implemented solution is not very robust.

A better solution may be to implement hygiene using lexical closures.  I 
suspect syntax-case uses some variant of the latter.  I'd like to take some 
time out and clean up macro handling in Kawa, including solid 
let-syntax/letrec-syntax support, fixing quote handling, and useful (maybe 
complete) support for implementation.  I'd prefer to defer this bug until then.













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