rec in kawa?

Sat Oct 7 08:32:04 GMT 2023

i have this definition but i miss rec in kawa:

;; scheme@(guile-user)> (def (foo) (when #t (return "hello") "bye"))
;; scheme@(guile-user)> (foo)
;;  "hello"

;; (def x)

;; (def (foo n)
;;      (cond ((= n 0) 'end0)
;;        ((= n 7) (return 'end7))
;;        (else (cons n (foo {n - 1})))))

;; scheme@(guile-user)> (foo 5)
;; (5 4 3 2 1 . end0)
;; scheme@(guile-user)> (foo 10)
;; (10 9 8 . end7)

;; (def (bar n)
;;      (cond ((= n 0) 'end0)
;;        ((= n 7) (return-rec 'end7))
;;        (else (cons n (bar {n - 1})))))

;; scheme@(guile-user)> (bar 5)
;; $4 = (5 4 3 2 1 . end0)
;; scheme@(guile-user)> (bar 10)
;; $5 = end7
(define-syntax def

  (lambda (stx)

      (syntax-case stx ()

    ;; multiple definitions without values assigned
    ;; (def (x y z))
    ((_ (var1 ...)) #`(begin (define var1 '()) ...))

    ;;  (def (foo) (when #t (return "hello") "bye"))
        ;; ((_ (<name> <arg> ...) <body> <body>* ...)
        ;;  (let ((ret-id (datum->syntax stx 'return)))
        ;;    #`(define (<name> <arg> ...)
    ;;        (call/cc (lambda (#,ret-id) <body> <body>* ...)))))

    ((_ (<name> <arg> ...) <body> <body>* ...)

         (let ((ret-id (datum->syntax stx 'return))
           (ret-rec-id (datum->syntax stx 'return-rec)))

       #`(define (<name> <arg> ...)

           (call/cc (lambda (#,ret-rec-id)

             (apply (rec <name> (lambda (<arg> ...)
                          (call/cc (lambda (#,ret-id) <body> <body>*
...)))) (list <arg> ...)))))))

    ;; single definition without a value assigned
    ;; (def x)
    ((_ var) #`(define var '()))

    ;; (def x 7)
    ((_ var expr) #`(define var expr))

    ((_ err ...) #`(syntax-error "Bad def form"))

    )))

any idea of replacement for it?