Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!elroy.jpl.nasa.gov!decwrl!pa.dec.com!src.dec.com!kalsow
From: kalsow (Bill Kalsow)
Newsgroups: comp.lang.modula3
Subject: Re: names of methods and instance variables of OBJECTs
Message-ID: <9104221550.AA03978@jumbo.pa.dec.com>
Date: 22 Apr 91 15:50:52 GMT
Lines: 35
In-Reply-To: Message of 20 Apr 91 19:16:44 GMT
    from buschman@tubsibr.uucp (Andreas Buschmann)
    <1991Apr20.191644.11028@tubsibr.uucp>
To: m3
Cc: buschman@tubsibr.uucp (Andreas Buschmann), kalsow

>  If I declare a type A beeing an OBJECT with a field named x and a
>  method named y, am I allowed to declare B beeing A OBJECT with a field
>  named y and a method named x, or only one of them?

Yes, the following is legal:

    TYPE A =   OBJECT x: INTEGER METHODS y () END;
    TYPE B = A OBJECT y: INTEGER METHODS x () END;

>  In the report I find:
>  
>  	The names introduced in FieldList and MethodList must be	(1)
>  	distinct.
>  
>  	...
>  
>  	A field or method in a subtype masks any field or method with	(2)
>  	the same name in the supertype. To access such a masked field,
>  	use NARROW to view the subtype variable as a member of the
>  	supertype. 

>  so does (1) include the names used in the super classes or not? And
>  why? 

No, "FieldList" and "MethodList" are names for syntactic pieces of an object
declaration.  They are not the set of all field or method names in the object.

>  The following example compiles ok, but terminates while running with:
>  fatal error: can't open display ''

Usually, "can't open display" indicates that your program cannot contact
an X server.  I doubt it's a Modula-3 problem.


  - Bill Kalsow