Re: syntax? in scheme/Guile

[Damien Mattei]

possible solution:


(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 >


;; scheme@(guile-user)> (syntax? #'(1 . 3))
;; $30 = #t

;; scheme@(guile-user)> (syntax? #'(1 2 3))
;; $28 = #t

;; scheme@(guile-user)> (syntax? #'*)
;; $23 = #t
;; scheme@(guile-user)> (syntax? 3)
;; $24 = #f
;; scheme@(guile-user)> (syntax? "")
;; $25 = #f


On Mon, May 13, 2024 at 10:42 AM Damien Mattei <damien.mattei@gmail.com>
wrote:

> hello,
>
> any idea for a predicate for syntax object in Guile/scheme like exist in
> Racket 'syntax?' ?
>
> i'm started writing something but i do not understand this part of R6RS:
>
> https://www.r6rs.org/final/html/r6rs-lib/r6rs-lib-Z-H-13.html#node_sec_12.2
>
> what examples can be done for :
>
>    -
>
>    -a nonpair, nonvector, nonsymbol value, or
>    -
>
>    -a wrapped syntax object.
>    - what is a wrapped syntax object?
>
>
> Damien
>
>
>
>    -
>
>