Re: expression and definition context in Scheme

[Damien Mattei <damien.mattei@gmail.com>]

i finalize my ideas about 'controls' and loops (with break and continue, as
while feature them ,even if scheme and macro do not allow ? (if someone
else have idea and solution about it?) implements of 'continue and 'break
because hygiene forbid it)
https://github.com/damien-mattei/library-FunctProg/blob/master/while-do-when-unless.scm

;; scheme@(guile-user)> (for/break-cont break continue ({i <+ 0} {i < 5} {i
<- {i + 1}}) {x <+ 7} (display x) (newline))
;; 7
;; 7
;; 7
;; 7
;; 7

;; scheme@(guile-user)> (for/break-cont break continue ({i <+ 0} {i < 5} {i
<- {i + 1}}) {x <+ 7} (display x) (newline) (break))
;;7

;; scheme@(guile-user)> (for/break-cont break continue ({i <+ 0} {i < 5} {i
<- {i + 1}}) {x <+ 7} (continue) (display x) (newline) (break))

(define-syntax for/break-cont

  (syntax-rules ()

    ((_ <break-id> <continue-id> (init test incrmt) b1 ...)

     (call/cc (lambda (<break-id>)
(let ()
 init
 (let loop ()
   (when test
 (call/cc (lambda (<continue-id>) b1 ...))
 incrmt
 (loop)))))))))

https://github.com/damien-mattei/library-FunctProg/blob/master/for-next-step.scm

Damien

On Thu, Sep 1, 2022 at 10:21 PM Damien Mattei <damien.mattei@gmail.com>
wrote:

> On Wed, Aug 31, 2022 at 5:29 PM Maxime Devos <maximedevos@telenet.be>
> wrote:
>
>>
>> On 31-08-2022 09:01, Damien Mattei wrote:
>> > I always try to keep compatibility with RnRS and in fact except cond
>> > none of when, unless, cond, case, while, and do are in standart RnRS
>> schem
>>
>> 'when', 'unless' and 'do' are actually RnRS, see (rnrs control).
>>
>
> oh your're right...i was sticked to R5RS ,time i was student...
>
>>
>> 'case' is also RnRS, see (rnrs base).
>>
>> However, looking at (guile)while do, 'while' is indeed non-standard.
>>
>
> and i had rewritten last week a 'while ... do' like in C or Pascal:
> https://www.tutorialspoint.com/pascal/pascal_while_do_loop.htm
> https://www.tutorialspoint.com/cprogramming/c_while_loop.htm
>
> in my Scheme+:
>
> ;; (define do '())
> ;; (while {i < 4}
> ;;    do
> ;;      (display i)
> ;;      (newline)
> ;;      {i <- {i + 1}})
> ;; 0
> ;; 1
> ;; 2
> ;; 3
> ;; $1 = #f
> (define-syntax while
>   (syntax-rules (while do)
>     ((_ pred do b1 ...)
>      (let loop () (when pred b1 ... (loop))))))
>
> i will have to forget it! as i want to keep compatibility with standard
> Scheme also but i will rewrite all with (let () ...) instead of (begin ...)
> unless it can cause some incompatibilities, for now , i do not see problems
> as "who can do more can do less"......
>
> Regards,
> Damien
>
>>
>>