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In article <9204072208.AA14964@internal.apple.com> Modula2 List <INFO-M2%UCF1VM.BITNET@cmsa.Berkeley.EDU> writes:
>In Oberon-2, variables can be exported as 'read-only' (by adding "-" instead of
>"*" in its declaration).  What constraints are imposed on the usage of this
>kind of variables while being imported?  Surely it cannot appear on the left
>side of an assignment statement.  But can it be passed as a VAR parameter to a
>procedure?

No. The variable is read-only.

>
>Why is the garbage collector a hindrance to the real time applications?  In the
>implementation to the run time environment, we can make the garbage collector
>as a concurrent process to the 'garbage producer', and find some way to ensure
>that the garbage producer does not produce garbage faster than the garbage
>collector can consume.  Are there any real language implementations using this
>kind of approach?  (Maybe some Ada implementations?)
>

There has been much work in the area of concurrent garbage collection. Papers
by Hans Boehm (now of Xerox PARC) come to mind, as well as Andrew Appel.
There are others as well. Not impossible to do, but sometimes very hard
rela time constraints (eg interrupts from device X must be handled within N
microseconds) where if you're in the middle of GC may be difficult to handle.

-- 
Chuck Lins, Apple Computer, Inc. Oberon-2 Paladin  lins@apple.com
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