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From: ags@pucc-i (Seaman)
Newsgroups: net.micro
Subject: Re: Arrays in Apple PASCAL Units? - (nf)
Message-ID: <240@pucc-i>
Date: Mon, 26-Mar-84 12:28:51 EST
Article-I.D.: pucc-i.240
Posted: Mon Mar 26 12:28:51 1984
Date-Received: Wed, 28-Mar-84 00:24:22 EST
References: <1138@inmet.UUCP>
Organization: Purdue University Computing Center
Lines: 40

The March, 1984 BYTE has an article on "Pascal's Design Flaws:  Modula-2
Solutions and Pascal Patches" by Mark C. Johnson and Allen Munro.  The
article lists "Pascal's Seven Deadly Sins" and demonstrates how each
of these problems is solved in Modula-2, and how Pascal programmers
can work around the problems.

One of the seven flaws in Pascal is, of course, the lack of open array
parameters.  In Modula-2, one can declare

		PROCEDURE Foo(VAR A : ARRAY OF Bar);

and have Foo compatible with all arrays of Bar, regardless of size or
index type.  As a special case, the declaration

		PROCEDURE Baz(VAR B : ARRAY OF WORD);

is compatible with any Modula-2 type (the actual parameter doesn't even
have to be an array type).

If you don't have Modula-2 on your Apple, there are at least two ways
to work around the problem.  One method, described in the article and
already mentioned on the net, involves a type "array[0..0] of bar",
disabled range checking and some games with variant records.

Another method is available in Apple Pascal if you are willing to write
the library routine in assembly language.  Just declare it

		procedure Baz(var B); external;

and it will be compatible with any variable (regardless of type), just
like the Modula-2 declaration above.  Unlike the Modula-2 procedure, your
assembly language routine won't be able to find out how large the actual 
parameter is unless you pass that information as another parameter.
-- 

Dave Seaman
..!pur-ee!pucc-i:ags

"Against people who give vent to their loquacity 
by extraneous bombastic circumlocution."