Similarly, you can represent safe functions as applicable structures (so
they can behave like functions) with a custom printing method.
#lang racket
(struct safe-function (f name)
#:property prop:procedure 0 ; first field is the function
#:methods gen:custom-write
Perhaps you want something like this:
Welcome to Racket v6.0.0.1.
> (current-print (lambda (x) (if (procedure? x) (printf "~a" (object-name x))
> (print x)) (newline)))
#
> +
+
> 10
10
On Jan 4, 2014, at 6:40 PM, Rian Shams wrote:
> Sorry for my lack of clarity.
>
> My question is about t
So obvious. Why I never thought of it, I don't know.
Clearly, I was stuck on wondering why there was no setter/getter for the
callback field. Just one level of indirection...
Cheers,
Matt
On Sat, Jan 4, 2014 at 5:55 PM, Matthias Felleisen wrote:
>
> It is trivial to switch the callback's behav
It is trivial to switch the callback's behavior at run-time:
#lang racket/gui
(define f (new frame% [label "test for Matt"]))
(define b (new button%
[label "hello world"]
[parent f]
[callback (lambda (b e) (indirect-callback b e))]))
(define (cb1 b
Yes, you need two functions: one that gives you the name of a procedure and one
that picks a procedure. I was merely hinting at how to do the former. --
Matthias
On Jan 4, 2014, at 4:57 PM, Rian Shams wrote:
> Thanks Matthias,
>
> If I use your definition:
>
> (define (select-random-safe-f
On Jan 4, 2014, at 1:30 PM, lothar atheling wrote:
> hello,
>
> is there a way to replace all the choices at one whack?
>
> i have choice lists several hundred items long, which to reset with
> choice% methods clear, append will be tedious
>
> the only way i can see is to work on a parent ar
Hi all,
I've wondered about this for a while, but never asked.
When I create a GUI widget, I attach a callback:
(define b (new button% [... ...] [callback (lambda (b e) ...)] ...))
Is it possible to attach a callback at runtime? The docs say "no," but I
thought I'd ask regardless. Perhaps what
Thanks Matthias,
If I use your definition:
(define (select-random-safe-function)
(object-name
(list-ref safe-function-set (random (length safe-function-set)
then,
>(procedure-arity (select-random-safe-function))
error:procedure-arity: contract violation
expected: procedure?
given:
hello,
is there a way to replace all the choices at one whack?
i have choice lists several hundred items long, which to reset with
choice% methods clear, append will be tedious
the only way i can see is to work on a parent area-container% with
change-children, but that also looks tedious.
it
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!)))
Sorry to hijack the thread. There are two features that I like, but
make DrRacket slow.
One is the Program Contour. I use it in my desktop computer, but I
have to disable it in my netbook.
Another one is the rounded highlighting of words in the find/replace
window. I usually keep it closed to gai
If you really just want the name, use object-name:
(define (select-random-safe-function)
(object-name
(list-ref safe-function-set (random (length safe-function-set)
Welcome to DrRacket, version 6.0.0.1--2013-12-29(bbb0c5f6/d) [3m].
Language: racket.
> (select-random-safe-function)
'$*
12 matches
Mail list logo
