Hey users, I'm experimenting with some simple games using big-bang from
2htdp/universe and I keep running into stuttering problems. It seems to be
the garbage collector slowing things down (green recycle symbol in drracket
is on whenever the program is frozen).
Increasing the memory limit or remov
I'm assuming you mean parametric contracts instead of polymorphic. But
not sure why those would be the correct solution, I think any/c would
work, I'm not seeing a case where wrapping the value would protect
anything.
I don't see a fundamental limitation to doing this either.
On Tue, Aug 6, 2013
yes, but I was curious about doing that during a debug session. Attempting
to set! a procedure to a lambda results in:
application: not a procedure;
expected a procedure that can be applied to arguments
given: '(lambda (x) (..))
arguments...:
...
so the 'New value for f' dialog input is interp
> I had exactly the same confusion back when I first tried it. Your
> example is really helpful. Could it be added to the docs for make-pipe
> and/or g(un)zip-through-ports?
Go for it. I think that's one of the few problems I tend to have with
Racket's documentation is a lack of examples. Functio
That's not a good solution. It works in your current example, but there
will be many possible cases where it won't. You're asking the macro system
to use whatever is currently bound to the name "dog^" in the context the
user wants to bind a name. That won't always be the dog^ interface, if
your
If this is your code in th edef window:
#lang racket
(define (f x) x)
(set! f f)
you can do this in the REPL:
Language: racket.
> (f 10)
10
> (set! f (lambda (x) (+ (sqrt x) 20)))
> (f 10)
23.162277660168378
>
On Aug 6, 2013, at 4:03 PM, Edgar Honing wrote:
> Hi,
> Is it possible to set!
The concept is pretty opaque; syntax object contexts are a fairly tricky,
black-magic part of the language. There is a rhyme and reason to them, but
it isn't terribly high level or user-friendly. Sadly, no one yet knows how
to do better for macros as powerful as Racket's. I've spent a long time
By the way, I found that this also works - applying the lexical context of
the dog-unit syntax-object to the dog^ identifier:
(define-syntax (use-dog stx)
(syntax-case stx ()
([_ dog-unit]
#`(define-values/invoke-unit dog-unit
(import)
(export #,(datum->syntax #'dog-un
Many thanks !
The problem makes sense and the solution works.
Are there any explanations of "syntax marks" beyond those in the "Syntax
Model" section of the documentation ? The concept seems opaque.
On Tue, Aug 6, 2013 at 2:32 PM, Carl Eastlund wrote:
> Nick,
>
> The unit system has some non
Hi all,
Does anyone know why Typed Racket does not support importing polymorphic
structs using the #:struct keyword in `require/typed`? Is this a
fundamental limitation or just a "small matter of programming"?
i.e., I want to do something like
(require/typed lang/posn
[#:struct posn (A) ([x
Nick,
The unit system has some non-hygienic behavior, by design. That is, it
introduces names that aren't part of its input, which isn't the default
behavior of hygienic macros. Of course we want this -- we want the macro
use-dog to bind the names woof and bark, which aren't directly part of its
The problem is that define-values/invoke-unit uses the lexical context
of its own syntax to associate the new identifiers with, so the new
identifiers aren't in the same context as the 'woof' use.
On Tue, Aug 6, 2013 at 3:11 PM, Nick Main wrote:
> I am attempting to write a macro to clean up the
Hi,
When generating pdf with the very useful slideshow-latex, equations have a
very poor quality.
Has anyone found a solution to this by any chance?
Test case (slidetex.rkt):
#lang slideshow
(require slideshow/latex)
(slide ($ "\\sum_{x\\in {\\cal X}} x^2"))
Then
slideshow --trust --pdf slidet
I am attempting to write a macro to clean up the use
of define-values/invoke-unit and finding some confusing behavior.
My macros module is:
#lang racket
(provide (all-defined-out))
(define-signature dog^
(woof
bark))
(define mutt@
(unit
(import)
(export dog^)
(define (woof) (
Hi,
Is it possible to set! other values than a string or a number using the
set! dialog in DrRacket while in debug mode? For example: I was wondering
whether a procedure value can be reassigned to another procedure/lambda.
Thanks much,
Edgar
Racket Users list:
http://lists.
On 08/06/13 19:07, Jay McCarthy wrote:
If you decide to create a Racket package (rather than a Planet
package) for your software and host it on Github, then only files you
explicitly add to the repository will be included in the package. More
details can be found here:
http://docs.racket-lang.or
On 08/06/13 16:32, Neil Van Dyke wrote:
Lawrence Woodman wrote at 08/06/2013 11:15 AM:
So I now know what will be in the archives, but is there anyway of
restricting
what goes into a package?
If you use McFly to build your PLaneT archive file, there is a feature
for this. The "mcfly-files"
I'll let Ryan comment on dynamic-wind usage. (I'd probably just use
with-handlers and raise.)
A couple optional thoughts:
1. I notice that with-gzip and with-gunzip are identical except for
the function they call. You could parameterize that away: Replace both
with a single `with-pipe` function t
If you decide to create a Racket package (rather than a Planet
package) for your software and host it on Github, then only files you
explicitly add to the repository will be included in the package. More
details can be found here:
http://docs.racket-lang.org/pkg/
Jay
On Tue, Aug 6, 2013 at 9:15
I had exactly the same confusion back when I first tried it. Your
example is really helpful. Could it be added to the docs for make-pipe
and/or g(un)zip-through-ports?
Racket Users list:
http://lists.racket-lang.org/users
I've never actually used dynamic-wind, although it does look interesting /
like what I need. A few questions / caveats though:
- Should the pipe be created in the pre-thunk or before the
dynamic-windentirely? The thunks don't seem to share scope, so I'm
guessing the latter,
but that seems a bit od
You might consider using dynamic-wind instead of that with-handlers. Or,
instead of (error 'with-gunzip ...) just do (raise exn). That way you won't
lose the stack information in the original exception (which is likely the
one a user would want).
Robby
On Tue, Aug 6, 2013 at 10:40 AM, JP Verkamp
Figured it out and cleaned it up. It turns out that I was using
with-handlers oddly, but reading further though the documentation it works
as expected. Here's a new version (generalized to any input-port):
(define (with-gunzip thunk)
(define-values (pipe-from pipe-to) (make-pipe))
(with-handle
Lawrence Woodman wrote at 08/06/2013 11:15 AM:
So I now know what will be in the archives, but is there anyway of
restricting
what goes into a package?
If you use McFly to build your PLaneT archive file, there is a feature
for this. The "mcfly-files" variable that "raco mcfly init" creates i
Hello,
I'm having problems omitting files when creating packages with:
raco planet create .
running from the root of the package directory.
As you can see from the mess I have made of:
http://planet.racket-lang.org/package-source/lwoodman/xdgbasedir.plt/1/0/
Which contains my swap files. I
Thanks Matthias for the #%app idea. This appears to work exactly as I had
wanted such that a hash in function position works with one arg. In the rare
case where my application does not want the default #f, I'll just use
(hash-ref) in the normal fashions.
(module my-racket racket
(provide
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