Thank you very much! That was exactly what I needed.
(define (reset-flowers flowers)
[when (method-in-interface? 'snap-back-after-regions? card<%>)
;; See Animations in the README file and see also
;; "mred/15064" in Racket's bug database. This is
;; conditional for compatibility with Rkt < 6.2.1
(broadcast flowers snap-back-after-regions? #t)]
(broadcast* flowers
(face-down)
(dim #f)
(user-can-flip #f)
(snap-back-after-move #t)
(user-can-move #f))
I'm a little bit astonished that Racket doesn't offer a defined? primitve when
it's not
possible to implement it with macros because of the strange compile-time
behavior.
Where compile time sound to me like put all the interned things together, call
it
byte code and dump it into a file.
Il giorno 24/mag/2015, alle ore 10.14, Laurent ha scritto:
> This may be of interest to you:
> http://stackoverflow.com/questions/20076868/how-to-know-whether-a-racket-variable-is-defined-or-not
>
> For methods, you can use this instead:
> http://docs.racket-lang.org/reference/objectutils.html?q=method-in#%28def._%28%28lib._racket%2Fprivate%2Fclass-internal..rkt%29._method-in-interface~3f%29%29
>
> For fields you can use:
> http://docs.racket-lang.org/reference/objectutils.html?q=method-in#%28def._%28%28lib._racket%2Fprivate%2Fclass-internal..rkt%29._field-names%29%29
>
> On the contrary to undefined identifiers, using an inexistant method will not
> cause any error until it is called.
>
> Laurent
>
> On Sun, May 24, 2015 at 8:20 AM, Michael Tiedtke
> <michael.tied...@o2online.de> wrote:
> I'm used to check for the presence of a definition of a given symbol with
> (defined? symbol)
>
> Probably I still remember that from GNU Guile Scheme but I was not able
> to find an equivalent in Racket.
>
> I need something like that to check during runtime or at least at start-up
> for the existence of a definition before using it. In particular I will need
> to
> check for the presence of a given field or method by name/symbol in
> an interface / class definition imported via require.
>
> Any ideas on how to do this with Racket?
>
> Then I'm afraid that Racket is going to lament the usage of an undefined
> symbol even though that part of code might never be reached because
> I had already checked for the presence of its definition.
>
> Example:
> In version 6.7 the /card-table/ class features a flag
> /call-handlers-after-snap-back/
> but version 6.5 does not have that flag. When the flag and its corresponding
> accessors
> are available it should use them, i.e. branch into parts of the code that can
> use them. If
> not they're not available it should ignore some parts / branches of the code.
>
> I can of course use /version/ to check for Racket's version but this doesn't
> take
> patches or third party libraries/modules into account.
>
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