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Path: utzoo!watmath!clyde!burl!mgnetp!ihnp4!houxm!mhuxl!ulysses!allegra!mit-eddie!genrad!decvax!ittvax!dcdwest!sdcsvax!sdcc6!loral!ian
From: ian@loral.UUCP
Newsgroups: net.lang.mod2
Subject: Re: Compiling Modula-2 in one pass?
Message-ID: <474@loral.UUCP>
Date: Thu, 6-Sep-84 11:23:16 EDT
Article-I.D.: loral.474
Posted: Thu Sep  6 11:23:16 1984
Date-Received: Wed, 12-Sep-84 03:19:33 EDT
References: <3432@decwrl.UUCP>, <57100006@hpfclo.UUCP>
Organization: Loral Instruments, San Diego
Lines: 47


   
   A previous article by Jacob Gore suggested that forward references
   in Modula are confined to references to procedures.  Mr. Gore suggests
   that since this is the case, a one pass compiler could be constructed,
   since only simple "back patching" of the symbol table would be
   necessary.  As discussed in a previous net article by Mike Powell,
   forward references are NOT confined to procedures.  The following
   program is allowed in Modula:

       MODULE ForwardReference;

	 PROCEDURE LookForward;
	 BEGIN
	   SomeHairyRec.Num := 0;
         END LookForward;

       VAR  (* note that this is global scope *)
	 SomeHairyRec : RECORD
			  Num : INTEGER;
			  AString : ARRAY[ 0..79 ] OF CHAR;
			  TheRealThing : REAL;
                        END;
       
       BEGIN
	 LookForward; 
       END ForwardReference.

   Please forgive any syntax errors, I don't have a Modula compiler on the
   VAX I use.

   Note that the statement which sets the record field to zero can not be
   checked until the record is entered in the symbol table.  No reasonable
   amount of "back patching" can take care of this problem.

			    Ian Kaplan
			    ucbvax!sdcc3!loral
			    Loral Data Flow Group
			    Loral Instrumentation
			    8401 Aero Dr.
			    San Diego, CA
			    92123
			    (619) 560-5888 x4812

                      PS: note name change of UC San Diego UNIX
			  Systems (i.e., sdccsu3 => sdcc3).