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From: bill@ibmpcug.co.uk (Bill Birch)
Newsgroups: comp.lang.lisp,connect.audit
Subject: Re: Memory Management in Lisp?
Message-ID: <1991Feb20.150947.2039@ibmpcug.co.uk>
Date: 20 Feb 91 15:09:47 GMT
Organization: The IBM PC User Group, UK.
Lines: 28

> An interesting idea, but potentially very dangerous.  An object may have
> references that the application isn't aware of.  For instance, the user
> could have assigned an object to a global variable while in the debugger.
> Or in a Dynamic Windows or CLIM environment, just printing out the object
> creates a new reference to the object from the window's output history
> structure.
> 
This is a function of the way garbage collection is arranged. A mark-
sweep system has problems with the above.However, in a reference-
counting LISP system, the total number of references to any object is
known by definition. Thus it is possible to allow the application
to garbage collect explicitly. 

For example I have an interpreter
that allows the programmer to read the reference count of an object.
Also , to force collection of an unused tree hanging off a symbol can 
simply be done by : (SETQ FOOBAR NIL) 

Since the reference count on
the contents of FOOBAR will have dropped to zero, the memory
is automatically reclaimed.

Bill
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Automatic Disclaimer:
The views expressed above are those of the author alone and may not
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