good... thank, it works, i do not know a lot about 'prompts , a good explanation is here:
https://stackoverflow.com/questions/29838344/what-exactly-is-a-continuation-prompt i personally find a solution too: (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")) ))) example: ;; scheme@(guile-user)> (foo 5) ;; $2 = (5 4 3 2 1 . end0) ;; scheme@(guile-user)> (foo 10) ;; $3 = (10 9 8 . end7) ;; scheme@(guile-user)> (bar 5) ;; $4 = (5 4 3 2 1 . end0) ;; scheme@(guile-user)> (bar 10) ;; $5 = end7 (def (foo n) (cond ((= n 0) 'end0) ((= n 7) (return 'end7)) (else (cons n (foo {n - 1}))))) (def (bar n) (cond ((= n 0) 'end0) ((= n 7) (return-rec 'end7)) (else (cons n (bar {n - 1}))))) the important part of this macro being: ((_ (<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> ...))))))) but i admit i had a chance to find this solution, i did it a bit like a blind man... but after all: “A mathematician is a blind man in a dark room looking for a black cat which isn’t there.” -- Charles Darwin Best regards, Damien On Wed, Nov 9, 2022 at 6:55 PM Olivier Dion <olivier.d...@polymtl.ca> wrote: > On Wed, 09 Nov 2022, Damien Mattei <damien.mat...@gmail.com> wrote: > > but in the general case , i want a macro that can do it on any function > > (i'm not sure it can be done because the continuation have to be captured > > just before the call to the function and be inlined at the good > > place....) > > I'm not aware of any control mechanism that are implicit in Guile. You > almost always have to deal with a continuation object. However, nothing > prevent you to invent your own control flow wrapper. > > For example: > --8<---------------cut here---------------start------------->8--- > (define my-prompt (make-prompt-tag)) > > (define-syntax-rule (return-now x) > (abort-to-prompt my-prompt x)) > > (define (wrap-this procedure) > (let ((inside? #f)) > (lambda args > (if inside? > (apply procedure args) > (begin > (set! inside? #t) > (let ((ret > (call-with-prompt my-prompt > (lambda () > (apply procedure args)) > (lambda (_ x) > x)))) > (set! inside? #f) > ret)))))) > > (define-syntax define-interruptible > (syntax-rules () > ((_ (name formals ...) body ...) > (define name > (wrap-this > (lambda (formals ...) body ...)))))) > > (define-interruptible (foo n) > (cond > ((= n 0) 'end0) > ((= n 7) (return-now 'end7)) > (else > (cons n (foo (1- n)))))) > > (pk (foo 5)) > (pk (foo 10)) > --8<---------------cut here---------------end--------------->8--- > > There's probably other way of doing so that I'm not aware of. > > -- > Olivier Dion > oldiob.dev >
