Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!tank!dwayne@rover.bsd.uchicago.edu
From: dwayne@rover.bsd.uchicago.edu
Newsgroups: comp.lang.pascal
Subject: Extended Pascal
Message-ID: <1997@tank.uchicago.edu>
Date: 24 Feb 89 16:22:49 GMT
Sender: news@tank.uchicago.edu
Organization: University of Chicago - Biomedical Physics
Lines: 60

What's wrong with the way VAX Pascal uses modules.  It's terribly easy to
use and it's very powerful.

In the program that you are writing, you properly declare your procedures
near the beginning of the program with the 'extern' qualifier.  This tells
the compiler to check each occurrence of the thing in your program, and
to check the types also.

For example:

PROGRAM TEST (INPUT,OUTPUT);
CONST...
TYPE...
VAR
    Y:	INTEGER;

PROCEDURE WHATEVER(VAR:X:INTEGER);EXTERN;

BEGIN
.
    WHATEVER(Y);
.
END.


At somepoint you create another file somewhere called a module.
It looks like:

MODULE MISCFNS (anyname) (INPUT,OUTPUT);

[GLOBAL] PROCEDURE WHATEVER(VAR X:INTEGER);
    BEGIN
    .
    .
    END;

END.

IF BOTH THE PROGRAM IS COMPILED AND THEN THE MODULE(S) ARE COMPILED...
WITHOUT ERROR OF COURSE, THEN YOU JUST LINK THEM:

LINK WHATEVER,MISCFNS

THEN THE VAX LINKER RESOLVES THE REFERENCES AND PRODUCES THE WHATEVER.EXE FILE.

THIS MAKES IT TERRIBLY CONVENIENT TO MAKE, FOR EXAMPLE, A MODULE CONTAINING A
BUNCH OF FUNCTIONS YOU LIKE TO  USE.  THEN WHENEVER YOU WRITE A PROGRAM THAT
USES ANY OF THEM THEN JUST LINK TO THAT MODULE.

LINK MYNEWPROG,MYFAVFNS

THIS OF COURSE USES THE VAX LINKER WHICH LINKS PROGRAMS AND MODULES REGARDLESS
OF THEIR NATIVE LANGUAGE (FOR EXAMPLE A C PROGRAM WITH FORTRAN AND PASCAL
FNS IF YOU LIKE).  BUT THE STANDARD COULD REQUIRE THE COMPILER TO PRODUCE
CROSS-REFERENCE TABLES OF UNFULFILLED REFERENCES. AND ALSO REQUIRE SOME
STANDARD LINKING PROTOCOL THAT TAKES THESE COMPILED OBJECT CODE FILES
AND RESOLVES THEM INTO EXECUTABLES.

DWAYNE SPRADLIN
DWAYNE@ROVER.BSD.UCHICAGO.EDU