[racket] Help: Passing a class to a macro and not an identifier

On Wed, Sep 15, 2010 at 15:59, Matthias Felleisen <matthias at ccs.neu.edu>wrote:

>
> Where do you want to bind them? In the current namespace? Scope?
>


Module scope, in the current namespace, runtime phase.
(I think, if I understand all these terms correctly).

Here is the same code as the previous one, but this time working (still only
for a%):

<a.rkt>
#lang racket

(provide a%)

(define a%
  (class object% (super-new)
    (init-field val)

    (define/public (get-the-val)
      val)
    ))


<singleton.rkt>
#lang racket

(require (for-syntax racket/class)
         "a.rkt"
         (for-syntax "a.rkt")
         )

(define-syntax-rule (define-singleton-sender func obj meth)
  (begin (printf "define-sender: ~s ~s ~s\n" 'func 'obj 'meth)
         (define (func . args)
           (send/apply (obj) meth args))))

(define-syntax (class->singleton stx)
  (syntax-case stx ()
    [(_ cl obj)
     (with-syntax ([(name ...)
                    (map (λ(n)(datum->syntax #'cl n))
                         (interface->method-names (class->interface a%)))])
; only for a% ***
       #'(begin (define-singleton-sender name obj name)
              ...))]))


(define current-a (make-parameter (new a% [val 3])))

(class->singleton a% current-a)

(get-the-val)



I really only need to pass some class to the class->singleton macro.
There must be some simple answer ; I'd be very surprised if this was not
possible.

Thanks a lot for the time you take to answer.




>
>
> On Sep 15, 2010, at 9:47 AM, Laurent wrote:
>
> >
> >
> > On Wed, Sep 15, 2010 at 15:29, Matthias Felleisen <matthias at ccs.neu.edu>
> wrote:
> >
> >
> > Would this help you:
> >
> > #lang racket
> >
> > (define a%
> >  (class object%
> >    (init-field this.x)
> >    (define/public (foo x)
> >      (set! this.x x))
> >    (define/public (bar)
> >      this.x)
> >    (super-new)))
> >
> > (new a% [this.x 10])
> >
> > (define (generic-methods class%)
> >  (map (lambda (name) (list name (make-generic class% name)))
> >       (interface->method-names (class->interface class%))))
> >
> > (generic-methods a%)
> >
> > If I could pass the latter result to a macro that binds the names with
> the function automatically, yes,
> > but this seems to be exactly my initial problem, I think.
> >
> >
> >
> >
> >
> > On Sep 15, 2010, at 9:10 AM, Laurent wrote:
> >
> > >
> > >
> > > On Wed, Sep 15, 2010 at 14:57, Matthias Felleisen <
> matthias at ccs.neu.edu> wrote:
> > >
> > > Can we start from something simpler?
> > >
> > > The name of your macro suggests that you want something like this:
> > >
> > > (define one-and-only-one-instance
> > >  (new (class my-super% ...)))
> > >
> > > This creates a class and creates a single instance. Because class is
> nested
> > > in the call to new, there is no way to get another instance.
> > >
> > > Would this be what you want?
> > >
> > > Okay, let me explain what I want to do (the name is not really set in
> stone yet).
> > >
> > > There is a class a% defined somewhere, and an instance parameter
> > > current-a%-object of class a%.
> > > Suppose a% has methods foo and bar.
> > >
> > > Then I call:
> > > (class->singleton a% current-a%-object)
> > >
> > > This is supposed to define the forms (foo ....) and (bar ....) so that
> they act like
> > > (send (current-a%-object) foo ....), etc.
> > >
> > > I want to build these definitions automatically from the methods of the
> class.
> > >
> > > Anyway, beside the intended goal, I'd still like to know how solve the
> macro issue.
> > >
> >
> >
>
>
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