Re: Porting to Java using Garden Point Compiler

From: [at]} <Stan>
Date: Wed, 17 Nov 2004 15:32:19 -0800

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Well, OK. I admit my previous solution was pretty much an off-the-wall
extreme OO solution with a bad interface. But, how about the following?
This solution is identical to the traditional way of passing a
function, and
is a better solution than my previous one. Here is the server:

=====================================================
MODULE NumericalProcessor;
        IMPORT Math;

        TYPE
                Function* = POINTER TO ABSTRACT RECORD END;

        PROCEDURE (f: Function) ValueOf* (x: REAL): REAL, NEW, ABSTRACT;

        PROCEDURE Area* (f: Function; min, max, tol: REAL): REAL;
        BEGIN
                RETURN f.ValueOf (min) + f.ValueOf (max)
        END Area;

END NumericalProcessor.
=====================================================

And here is the client.

=====================================================
MODULE NumericalApplication;
        IMPORT NumericalProcessor, Math, StdLog;

        TYPE
                MyFunction = POINTER TO RECORD (NumericalProcessor.Function) END;
        
        PROCEDURE (f: MyFunction) ValueOf (x: REAL): REAL;
        BEGIN
                RETURN x * x
        END ValueOf;

        PROCEDURE Do*;
        VAR
                f: MyFunction;
        BEGIN
                NEW(f);
                StdLog.Ln;
                StdLog.Real( NumericalProcessor.Area(f, 3, 4, 0.001));
                StdLog.Ln
        END Do;

END NumericalApplication.
=====================================================

Still, the mechanism is inheritance. This is _so_ close to the
traditional
way of passing a function, that porting a library should be fairly
mechanical.
My point is that procedure types are redundant, and it is the spirit of
Oberon
to not have more than one way to accomplish a task. There was even
a battle to include the FOR statement in the language because it is not
necessary as long as you have a WHILE. I also agree with Skulski's
devil's-advocate comment that function variables should be at a lower
level and only used to communicate with platform-specific routines. I
still maintain that high-level applications like numerical libraries
should
be packaged similarly to the above client/server system and that
procedure
parameters should not be in the language definition.

Cheers,
Stan

  J. Stanley Warford
Professor of Computer Science
Pepperdine University
Malibu, CA 90263
Stan.Warford{([at]})nowhere.xy
310-506-4332

On Nov 17, 2004, at 1:40 PM, Rex Couture wrote:

> ??? Thanks for clarifying how it can be done, but I'm with
> Wojtek Skulski on this one. First, it is much longer than my example,
> and therefore harder to read.
>
> More importantly, in your example I had a real problem
> figuring out that procedure Area used procedure ValueOf. This crucial
> information is not presented in the interface--you have to look inside
> the procedure. In my example, the procedural variable is clearly
> passed to the function (i.e., procedure), and this fact can be seen
> from a glance at the parameters. My example is also type-safe and
> robust.
>
> I'm not sure we're making any progress with fancy programming.
>
> Sincerely,
> Rex Couture

--------------------------------------------

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Received on Thu Nov 18 2004 - 00:32:19 UTC