Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!decwrl!pa.dec.com!src.dec.com!gnelson
From: gnelson (Greg Nelson)
Newsgroups: comp.lang.modula3
Subject: Re: language change wishes / Olivetti Modula-3 info needed
Message-ID: <9102052259.AA19394@jumbo.pa.dec.com>
Date: 5 Feb 91 22:59:26 GMT
Lines: 24
In-Reply-To: Message of Tue, 29 Jan 91 16:03:57 GMT
    from Marc Wachowitz <I403%DMAFHT1.BITNET@CUNYVM.CUNY.EDU>
    <9101291633.AA07621@decpa.pa.dec.com>
To: m3
Cc: Marc Wachowitz <I403%DMAFHT1.BITNET@CUNYVM.CUNY.EDU>
X-Folder-Carbon: sent


Marc Wachowitz suggests that "UNTRACED" should be a function from 
types to types; where "UNTRACED T" is like T, but not traced by the 
garbage collector.  For example,

TYPE 
  T = OBJECT n: INTEGER END;
  UT = UNTRACED T;
 
This would be useful if T was very long or defined in a different interface.  
Unfortunately, this doesn't work.  Consider

TYPE 
  T = OBJECT METHODS p := P END;

PROCEDURE P(self: T);

TYPE U = UNTRACED T;

What is the p method of U?  It can't be P, since the type of the 
first argument is wrong.  So it cannot be true that "UNTRACED T" is like 
T except that it is not traced by the garbage collector.  When this 
simple definition failed, the committee gave up on the idea that 
UNTRACED was a function from types to types.