[Bug-kawa] [bug #13821] problem with letrec and define-macro

[anonymous]

URL:
  <http://savannah.gnu.org/bugs/?func=detailitem&item_id=13821>

                 Summary: problem with letrec and define-macro 
                 Project: Kawa
            Submitted by: None
            Submitted on: Sat 07/16/2005 at 17:18
                Category: Scheme language
                Severity: 3 - Normal
              Item Group: Run-time exception
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open

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Details:

In some cases letrec doesn't seem to be working with define-macro.
I haven't been able to find out why sometimes it works and sometimes it
doesn't.

Here is a simple example that does not work (using the latest Kawa from
CVS):

(define-macro (a-test #!key (args ()))
  (letrec ((double (lambda (x) (* x 2))))
    `(+ ,@(map double args))))

When I try it:

#|kawa:84|# (a-test)
0
#|kawa:85|# (a-test args: ())
0
#|kawa:86|# (a-test args: (1 2 3))
java.lang.NullPointerException
        at atInteractiveLevel$37.lambda1$V(<stdin>:81)
        at atInteractiveLevel$37.applyN(<stdin>)
        at gnu.expr.ModuleMethod.applyN(ModuleMethod.java:207)
        at kawa.lang.Macro.expand(Macro.java:162)
        at kawa.lang.Macro.scanForm(Macro.java:193)
        at kawa.lang.Translator.scanForm(Translator.java:913)
        at gnu.kawa.lispexpr.LispLanguage.parse(LispLanguage.java:59)
        at kawa.Shell.run(Shell.java:203)
        at kawa.Shell.run(Shell.java:172)
        at kawa.Shell.run(Shell.java:159)
        at kawa.repl.main(repl.java:673)
<stdin>:86:1: evaluating syntax transformer 'a-test' threw
java.lang.NullPointerException

This behavior seems to be quite random: some define-macro very similar to this
one do work, but when I remove an unused (not called anywhere) lambda in the
letrec they stop working! Sometimes even removing part of an unused lambda
makes it fail. For example:

(define-macro (define-generator name #!key (fields ()) (generators ()))
  (letrec ((create-field
            (lambda (field)
              (if (pair? field)
                  `(,(first field) init-value: ,(second field))
                  `(,field init-value: ()))))

           (->slot-ref
            (lambda (x)
              (cond ((null? x) ())
                    ((pair? x)
                     (cons (->slot-ref (car x)) (->slot-ref (cdr x))))
                    ((symbol? x)
                     (if (member x fields)
                         `(slot-ref (this) ',x)
                         x))
                    (else x))))
           
           (create-generator
            (lambda (generator)
              (let ((gname (car generator))
                    (gbody (cdr generator)))
                `((,(string->symbol (string-append "gen-"
                                                   (symbol->string gname))))
                  ;(->string-append ,@(map ->slot-ref gbody)))))))
                  (->string-append ,@gbody))))))
    
    `(define-simple-class ,name ()
       ,@(map create-field fields)
       ,@(map create-generator generators))))

The I can do:

(define-generator some-test fields: (a b c))

and it works, but if I remove the unused ->slot-ref lambda then it fails!







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