-----Ursprüngliche Nachricht-----
Von: "John Cowan" <
cowan@...>
An: <
concatenative@yahoogroups.com>
Gesendet: Samstag, 31. März 2001 06:42
Betreff: [stack] My proposal for polymorphic/generic/overloaded user
functions in Joy
> "Dispatch" takes one quotation argument; however, the quotation is *not*
> executed. Instead, the strings naming the words of which it consists
> are concatenated in reverse order with "-" between them, and the symbol
> table is searched for a defined function with that name. If it exists,
> the stack is popped and it is executed. If no such definition exists,
> the stack is unconsed and we try again. When the stack top is a null
> list, "dispatch" signals an error.
So, you compose a string and seek an accordingly named function
every time a method shall be called? Sounds kinda slow.
In an OOP Extension to Forth, i defined constants for generic method
names, some way like this:
0 constant do
1 constant paint
2 constant delete
...
and for each object type, i created a list (a VMT) that contained
the addresses of the words, so namely, the VMT for type point
would look like
[ point-do point-paint point-delete ]
so i only had to do a table lookup. Plus, there was a mechanism
for name-mangling, like in your scheme, but it would build up
these tables during compile time so it's faster during runtime.
If you can't do it in compile-time in Joy, you could do it with
some "initializer" word during runtime.
BTW, my OOP-scheme for Forth is not completely satisfying,
at the moment it's invoked by saying
args method object
but it would be better to invoke it in the sequence
args object method
for some twisted reason... Actually, at the moment, my objects
are some kind of "magic" because they perform the dispatch...
so they don't mix very well with other data. The dispatch magic
should be part of the method word. (Like in your proposal, if i
understood it correctly)
Dirk Heise
What's a life and where do i get one?