Path: news.daimi.aau.dk!glad
From: "S\xren Brandt" <sbrandt@daimi.aau.dk>
Newsgroups: comp.lang.beta
Subject: Re: THIS and COMPONENTs
Date: 26 Jul 1996 12:25:45 GMT
Organization: DAIMI, Computer Science Dept. at Aarhus University
Lines: 84
Approved: mailtonews@daimi.aau.dk
Distribution: world
Message-ID: <4tadg9$smm@gjallar.daimi.aau.dk>
NNTP-Posting-Host: daimi.daimi.aau.dk

Ah, well. It seems that I misunderstood your request. Below is the requested
"objectToComponent". Please ignore that objectToComponent exploits undocumented 
low-level features of the compiler. If the entered object is not a component,
"objectToComponent" will return NONE.

   INCLUDE '~beta/sysutils/v1.4/objinterface';
   ---lib:attributes---
   objectToComponent:
     (# o: ^Object;
        c: ^|Object;
        ato: @addressToObject;
     enter o[]
     do (if o[]<>NONE then
            (if (o[]->getGCField)//-6 then
                (if ((@@o->tos'%AdrGetLong')-24->tos'%AdrGetLong')
                 //ComponentPTvalue then
                    (@@c,(@@o->tos'%AdrGetLong')-24)->assignRef
                if);
            if);
        if);
     exit c[]
     #);

   example:
     (# o: ^Process;
        c: ^|Process;
     do ...;
        o[]->objectToComponent->c[];
     #);

Hope this is of more help than my previous reply.

  -- Soren

> No, it is not.  I am not using the systems library, I am controlling
> the scheduling of the co-routines myself (which might be the wrong
> approach, but was what I wanted to do - to make the simulation
> scheduler directly).  I believe that there is no such mechanism (to
> obtain the currently executing co-routine), which is why the basic
> system library has a variable "theActive" (in my scheduler I called it
> currentEntity).
> 
> The BETA S.fork is now S[]->fork because it is not possible to write
> it as:
> System:
> (# ...
>    fork :
>    (# do ...
>          this(system)[] -> Scheduler.queue
>    #)
> #)
> 
> (Or whatever the scheduler is called).
> 
> Because Scheduler.queue will expect something qualified as
> "^|System[]" but this(system)[] is an item, not a component.
> 
> Therefore fork is implemented to recieve a co-routine reference,
> which avoids the problem of "casting" between items and components.
> 
> I would like to do "this(|System)[]" or similar.
> 
> But I hope there is a way anyway, it would look better.
> 
> In the "objinterface" library I have found the following two
> procedures. What I lack is the third which could have been named
> "objectToComponent"
> 
> isComponent: BooleanValue
>   (* Exits true if obj is a component. *)
>   (# obj: ^Object;
>   enter obj[]
>   <<SLOT isComponentBody:dopart>>
>   #);
> 
> componentToObject:
>   (* Exits the item part of the object entered *)
>   (# comp: ^|Object;
>      obj: ^Object;
>   enter comp[]
>   do <<SLOT componentToObjectBody:descriptor>>
>   exit obj[]
>   #);