Re: Message Passing with GOOPS

[Michael Tiedtke]

On 26/06/2015 10:18, Ralf Mattes wrote:
> ...
> > This is a first "raw" definition where the parameter /message/ has to be a
> > quoted symbol.
> >
> > (define-method (call (receiver <object>) message . arguments)
> >    (apply (slot-ref receiver message) arguments))
> >
> >
> > The class definition still looks like traditional GOOPS but it works.
> >
> > An example:
> >
> > (define-class <receiver> ()
> >    (msg #:init-value (lambda () 'hello-world)))
> >
> > (define r (make <receiver>))
> > (call r 'msg) => 'hello-world
> >
> >
> > Now I'd like to have an easier syntax for describing the slot. The
> > definition might be:
> >
> > (define-syntax define-message
> >    (syntax-rules ()
> >      ((_ (message-name arguments ... ) body ...)
> >       (message-name #:init-value (lambda (arguments ...) body ...)))))
> >
> > But the following example doesn't work in 1.8:
> >
> > (define-class <house> ()
> >    (define-message (phone n)
> >      (repeat n (lambda () (bell) 'rang)) ))
> >
> > GOOPS complains about malformed slots and *seems* to see the unexpanded
> > form.*
> Here:
>
>   $ guile-1.8
>   guile> (use-modules (oop goops))
>   guile> define-class
>   #<macro! define-class>
>
> Why would you expect a macro to evaluate its arguments? :-)
The use of macros within macros is yet to be evaluated. But as syntax 
transformers sometimes check their arguments before these expressions 
are expanded if they are macros - one should really think about Scheme's 
macro expansion model.

Do you think syntax transformers have in any way anything to do with the 
evaluation of code?


> > I could use a little help here, anyone?* Even for the naming scheme: /send/
> > is already used by unix sockets and methods are part of the implementation
> > of generics. Perhaps /message/ isn't that bad.
> That's what modules are for.
>
> guile> (define-module (ios) #:export (send))  ; ios = Inferior Object System
>
> and then:
>
> guile> (ios:send ....)

Yes, just call it r-0b-delta-36x7 and let people rename it to find out 
what it means.


> > [...]
> > PS
> > Perhaps it's better to recreate a clean object model without 3,000 lines of
> > C code like GOOPS. But then GOOPS really creates the illusion of an object
> > oriented environment with a MOP ...
> Why, 3000 lines of C code seems like a rather lean codebase for an objet system.

Seems like your sentence is not a valid expression in Scheme.