Path: utzoo!attcan!uunet!mcvax!unido!infbs!neitzel
From: neitzel@infbs.UUCP (Martin Neitzel)
Newsgroups: comp.lang.modula2
Subject: Re^2: Error in PD Modula-2 compiler? Or just in my brain?
Summary: Does spreading misinformation world-wide make fun
	to some people, or what?
Message-ID: <1231@infbs.UUCP>
Date: 28 May 89 22:16:19 GMT
References: <340@actisb.UUCP> <1090@gmdzi.UUCP>
Followup-To: comp.lang.modula2
Organization: TU Braunschweig,Informatik,West Germany
Lines: 31

kloppen@gmdzi.UUCP (Jelske Kloppenburg) writes:
JK>	
JK>	The type transfer in the TU Muenchen Modula2 is as follows:
JK>	FROM SYSTEM IMPORT VAL;  [...]
JK>	BEGIN ...  c:=VAL(CARDINAL,b); ....
JK>	
JK>	I learned it from reading some source in the package.

From reading Wirth's Modula2 report, [10.2 "Standard procedures"], you
might learn even more.

1. VAL is _not_ a "type transfer function" [pim3, 12.], but a standard
   procedure [pim3, 10.2].  Especially, VAL conversions guarantee to
   preserve the value, which may involve changes in the representation.
   Type transfers, on the other hand, do not.

2. Usage of VAL doesn't require SYSTEM.  (pim3: "Standard procedures are
   predefined.")

3. This VAL is constrained to some integral types and won't help in the
   original "TYPE Stack = List" problem.

4. It is a known ambiguity in the Modula2 report:  Can standard
   identifiers be redefined or not?  In procedures, definitely yes, but
   the situation in modules is not clear at all.  Depending on this
   ambiguity, the TU Muenchen compiler may or may not be considered
   PIM3-conforming  ("broken" is too harsh a word in this context).
   In any case, the compiler has to provide a standard procedure VAL in
   addition to the SYSTEM-VAL mentioned by you.

						Martin Neitzel