[racket] procedure to string

Thank you! I will try that. Sorry for the delayed response. Got caught up
in another project.


On Sat, Jan 4, 2014 at 9:40 AM, Gustavo Massaccesi <gustavo at oma.org.ar>wrote:

> There are more complex closures, that share an external variable. For
> example:
> ;-----
> #lang racket
> (define-values (up! down!)
>   (let ()
>     (define counter 0)
>     (define (up!) (set! counter (add1 counter)) counter)
>     (define (down!) (set! counter (sub1 counter)) counter)
>     (values up! down!)))
> (up!) ;==> 1
> (up!) ;==> 2
> (down!) ;==> 1
> ;-----
> If you need to send “up!” and “down!” in different interactions but
> they nevertheless have to modify the same counter then this problem is
> very difficult.
>
> For some cases, I guess that you can uses something similar to the
> “Stateless Servlets”
>
> http://docs.racket-lang.org/web-server/stateless.html#(part._considerations)
> . I didn’t use it, but it can serialize and deserialize functions and
> continuations. I don’t know how much transparent are the structures it
> use, so I’m not sure if it’s possible to inspect them. I’m not sure
> that you can deserialize the continuation in another server, but you
> can deserialize it after a server reboot, so I guess it’s possible.
>
> (And as Neil Toronto said, you should also use sandboxing to avoid
> unexpected problems.)
>
> Gustavo
>
>
> On Fri, Jan 3, 2014 at 5:10 PM, Neil Toronto <neil.toronto at gmail.com>
> wrote:
> > What kind of inspection?
> >
> > If it's for security purposes, you're better off running the procedures
> in a
> > sandbox (see the `racket/sandbox' module). You can even control the
> amount
> > of time something is allowed to run. Also, `serial-lambda' might be
> > something you could use, if the sender and receiver are both running the
> > same program. (It might work in other circumstances; I don't know.)
> >
> > Neil ⊥
> >
> >
> > On 01/02/2014 09:41 AM, Alegria Baquero wrote:
> >>
> >> Thank you for your kind responses. Your solutions are good ones but
> >> unfortunately don't fit my purpose. Imagine a mobile code scenario where
> >> you have no control of the definition of a closure. What I want to do is
> >> to be able to print the body of any incoming closure that arrives in a
> >> message. So if server A sends server B a closure (lambda () (displayln
> >> "hello world")), B could grab that incoming closure and capture it as
> >> the string "(lambda () (displayln "hello world"))" so it can be
> >> inspected before executing it. Does this make sense? How can I then
> >> construct a function procedure->string that transforms at runtime
> >> (without using macros) a closure's body to a string?
> >>
> >> Thank you again and happy new year.
> >>
> >> Alegria
> >>
> >>
> >> On Tue, Dec 31, 2013 at 10:53 AM, Alexander D. Knauth
> >> <alexander at knauth.org <mailto:alexander at knauth.org>> wrote:
> >>
> >>     Yes, you can do it with a struct with the property prop:procedure.
> >>
> >>     #lang racket
> >>
> >>     (require rackunit)
> >>
> >>     (struct my-proc (proc str)
> >>        #:property prop:procedure (struct-field-index proc))
> >>
> >>     (define f
> >>        (my-proc  (lambda (x) (+ x 1))
> >>                 "(lambda (x) (+ x 1))"))
> >>
> >>     (check-true (procedure? f))
> >>     (check-equal? (f 1) 2)
> >>     (check-equal? (my-proc-str f)
> >>                    "(lambda (x) (+ x 1))")
> >>
> >>     (define-syntax-rule (my-lambda args body ...)
> >>        (my-proc                 (lambda args body ...)
> >>                 (substring (~v '(lambda args body ...)) 1)))
> >>
> >>     (define f2
> >>        (my-lambda (x) (+ x 1)))
> >>
> >>     (check-true (procedure? f2))
> >>     (check-equal? (f2 1) 2)
> >>     (check-equal? (my-proc-str f2)
> >>                    "(lambda (x) (+ x 1))")
> >>
> >>
> >>     On Dec 29, 2013, at 10:45 PM, Alegria Baquero wrote:
> >>
> >>>     Hello,
> >>>
> >>>     is there any way to transform a function's body to a string such
> >>>     as "(lambda(x)...)"?
> >>>
> >>>     Thanks
> >>>
> >>>     Alegria
> >>>     ____________________
> >>>      Racket Users list:
> >>>     http://lists.racket-lang.org/users
> >>
> >>
> >>
> >>
> >>
> >> --
> >>
> >>
> ---------------------------------------------------------------------------------------
> >> PhD candidate
> >> Department of Informatics
> >> Donald Bren School of Information and Computer Sciences
> >> University of California, Irvine
> >>
> >>
> >> ____________________
> >>    Racket Users list:
> >>    http://lists.racket-lang.org/users
> >>
> >
> > ____________________
> >  Racket Users list:
> >  http://lists.racket-lang.org/users
>



-- 
---------------------------------------------------------------------------------------
PhD candidate
Department of Informatics
Donald Bren School of Information and Computer Sciences
University of California, Irvine
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