Re: syntax? in kawa/scheme

[Damien Mattei <damien.mattei@oca.eu>]

yes in kawa there is no difference in this example:

(equal? #'(1 2 3) '(1 2 3))
#t

i had written for scheme (guile) a predicate based on the parsing of 
display of an object but it will not work with kawa:

(define (syntax? obj)

   (cond ; a syntax object is:
    ((pair? obj) ; a pair of syntax objects,
     (and (syntax? (car obj))
      (syntax? (cdr obj))))
    ((list? obj)
      (every syntax? obj))
    ((vector? obj) ; a vector of syntax objects
     (every syntax? (vector->list obj)))
    ((string? obj) ; as i will use the string representation of object
     #f)
    ;; parse the representation of object to search for #<syntax something>
    (else (let* ((str-obj (format #f "~s" obj))
         (lgt-str-obj (string-length str-obj))
         (str-syntax "#<syntax")
         (lgt-str-syntax (string-length str-syntax)))
        (and (> lgt-str-obj lgt-str-syntax) ; first, length greater
         (string=? (substring str-obj 0 lgt-str-syntax)
               str-syntax) ; begin by "#<syntax"
         (char=? #\> (string-ref str-obj (- lgt-str-obj 1)))))))) ; last 
char is >

but in fact my problem is to test equality for 2 syntax object and i can 
not use equal? :

#|kawa:34|# (equal? #'* #'*)
#f

but bound-identifier=?


#|kawa:35|# (bound-identifier=?  #'* #'*)
#t
#|kawa:36|# (bound-identifier=?  #'* #'-)
#f

my problem is to test equality for operators in a syntax parser

but this does not works for every syntax object:


#|kawa:38|# (bound-identifier=? #'(1 2 3) #'(1 2 3))
java.lang.RuntimeException: bound-identifier-? - argument is not an 
identifier
     at kawa.standard.syntax_error.error(syntax_error.java:55)
     at kawa.lib.prim_imports.reportSyntaxError(prim_imports.scm:249)
     at kawa.lib.std_syntax.isBoundIdentifier$Eq(std_syntax.scm:312)
     at atInteractiveLevel-37.run(tty:38)
     at gnu.expr.ModuleExp.evalModule2(ModuleExp.java:290)
     at gnu.expr.ModuleExp.evalModule(ModuleExp.java:211)
     at kawa.Shell.run(Shell.java:289)
     at kawa.Shell.run(Shell.java:196)
     at kawa.Shell.run(Shell.java:183)
     at kawa.repl.processArgs(repl.java:724)
     at kawa.repl.main(repl.java:830)


so i must check a difference between the syntax object that have in 
their string representation #<syntax something > and others



Le 13/05/2024 à 16:59, Per Bothner a écrit :
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>
> On 5/13/24 5:20 AM, Damien Mattei wrote:
>> hello,
>>
>> any idea for a predicate for syntax object in Kawa/scheme like exist 
>> in Racket 'syntax?' ?
>
> One problem is that everything is a syntax object.
>
> You can check if an object implements kawa.lang.SyntaxForm, but other 
> objects are
> also allowed in syntax values, if they don't need an explicit 
> TemplateScope.