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using Orestis Vantzos OOP package

• To: mathgroup at smc.vnet.net
• Subject: [mg76872] using Orestis Vantzos OOP package
• From: Hannes Kessler <HannesKessler at hushmail.com>
• Date: Tue, 29 May 2007 04:54:48 -0400 (EDT)

Hello,

my question is related to difficulties to use Orestis Vantzos OOP
package (http://library.wolfram.com/infocenter/Conferences/5773/) in
other package files.

The following is from the OOP package
	MakeExpression[RowBox[{RowBox[{obj_, "::", msg_}], "[", args___,
"]"}], StandardForm] :=
		MakeExpression[RowBox[{obj, "[", RowBox[{"\"" <> msg <> "\"", "[",
args, "]"}], "]"}], StandardForm]

It gives the following interpretation rule for expressions typed in a
notebook
	obj::msg[args] -> obj["msg"[args]]
and allows you to write definitions similar to
	obj::msg[args] = 1

I saved the OOP package in a file OOP.m and loaded it with
Needs["OOP`"].
The first problem was the following complaint by Mathematica
	SetDelayed::"write" :  "Tag MessageName in super::"path"[] is
Protected."
resulting from the following line the OOP package
	super::path[] := $superPath;

The complaint disappears after changing changing this line to
	super["path"[]] := $superPath;
in agreement with the intended interpretation.

Loading the package and using it in a notebook works,
writing in class definitions expressions as for example
	volume[] := (4*Pi*self::radius[]^3)/3;

However, using class definitions in package files  causes problems.
Here is Vantzos Sphere-example written to TestSphere.m
	BeginPackage["TestSphere`", {"OOP`"}];
	BeginClass["Sphere`"];
	volume[] := 4/3 Pi (self::radius[])^3;
	translateBy[\[CapitalDelta]x_] := (self::center[] += \
[CapitalDelta]x);
	EndClass[];
	EndPackage[];

Loading the package to a notebook and using it leads to errors
	Needs["TestSphere`"];
	s1<=={"Sphere`", "Object`"};
	s1::radius[] = 1;
	s1::volume[]
--> 4/3 Pi self::"radius"[]^3
instead of the expected 4/3 Pi
	s1::center[] = {1, 0, 0};
	s1::translate[{2,0,0}]
--> Error message
	AddTo::"rvalue" :  "self::"center"[] is not a variable with a value,
so its value cannot be changed."
instead of the expected {3,0,0}

I suspected the above MakeExpression interpretation rule for boxes
does not function in plain text package files.

But attempting
	Unprotect[MessageName];
	MessageName[a_Symbol, b_String][args___] := a[b[args]]
	Protect[MessageName];
does not help either as it generates the error
	Message::"name" :  "Message name a_Symbol::b_String is not of the
form symbol::name or symbol::name::language."

Any suggestions how to use the OOP package in other package files?

Thanks in advance.
Hannes Kessler