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From: protonen@daimi.aau.dk (Lars J|dal)
Newsgroups: comp.lang.modula2
Subject: Re: definition module loops
Message-ID: <1991May13.110458.13833@daimi.aau.dk>
Date: 13 May 91 11:04:58 GMT
References: <1991May12.071720.29928@ibmpcug.co.uk> <76170@eerie.acsu.Buffalo.EDU> <1991May13.100833.13386@daimi.aau.dk>
Sender: protonen@daimi.aau.dk (Lars J|dal)
Organization: DAIMI: Computer Science Department, Aarhus University, Denmark
Lines: 53

I forgot to define a main program to use the modules. The modules should be

DEFINITION MODULE m1;
VAR x:CARDINAL;
END m1.

DEFINITION MODULE m2;
VAR y:CARDINAL;
END m2.

IMPLEMENTATION MODULE m1;
FROM m2 IMPORT y;
VAR x:CARDINAL;
BEGIN
   x:=1;
   y:=1;
END m1.

IMPLEMENTATION MODULE m2
FROM m1 IMPORT x;
VAR y:CARDINAL;
BEGIN
   x:=2;
   y:=2;
END m2.

MODULE main_program;
FROM m1 IMPORT x;
FROM m2 IMPORT y;
FROM InOut IMPORT WriteCard;
BEGIN
   WriteCard(x,0);
   WriteCard(y,0);
END main_program.

>If they are compiled in the above order the definition modules will not
>use anything undefined. The implementation modules know the type of the
>foreign variable (x or y), so there is no problem either. But it is
>undefined whether the body of m1 or m2 is executed first, so if one
>compiler ends up with x=1 and y=1, you have no guarantee another compiler
>will do the same.
So the output should be 11 or 22, but the one is as correct as the other.
>(Only Wirth know if that was what he meant so please correct me if I'm
>wrong :-) )

>Good luck with the implementation!

+--------------------------------------------------------------------------+
|      Lars J|dal       |       (put your favourite quotation here)        |
| protonen@daimi.aau.dk |                                                  |
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| Computer Science Department  -  Aarhus University  -  Aarhus  -  Denmark |
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