Re: anyone define port types?

[Jan Wedekind <jan@wedesoft.de>]

On Wed, 30 Mar 2016, Marko Rauhamaa wrote:

> Jan Wedekind <jan@wedesoft.de>:
>
>> GOOPS supports "open" classes and multiple-dispatch. E.g. you can extend
>> the "write" method to control how an object is displayed within the
>> Guile REPL [1]. Another interesting approach are multi-methods in
>> Clojure which don't even require explicit types for dispatching.
>>
>> [1] http://wedesoft.de/oop-with-goops.html
>
> Your example demonstrates my problem with GOOPS: you are redefining
> (display) by penetrating the black box with (slot-ref). What would
> happen to your method if I changed the implementation of <a> so it
> no longer has the slot x, even virtually.
>
> GOOPS' has the worst possible object model: objects are seen as mere
> data records. The concept of a "slot" is an anathema to OOP.
>
> Think of a UNIX file. You access it through open(2), write(2), read(2),
> close(2) and so on. You don't know and you shouldn't care how the file
> contents are organized on the disk (if there is a disk!). GOOPS would
> like to abandon the system calls and just expose the bytes (slots) on
> the disk. Then, GOOPS lets you define any kind of system calls you see
> fit.
>
>
> Marko
Ok, I have updated the example to use accessor functions instead of 
"slot-ref". But yes, a GOOPS generic only dispatches on types where 
instances in turn need to define slots (attributes). That's why I pointed 
out Clojure multimethods which uses a more flexible dispatch mechanism 
(using an inheritance graph and dispatching on the return value of an 
arbitrary function).

GOOPS (as well as Clojure multimethods) provide "open" classes and 
multiple-dispatch. Two things which I can really recommend to play with.