Re: invoking java from within octave and do overloading

[Michael Goffioul]

On Sun, Oct 31, 2010 at 3:09 PM, Ernst Reissner <address@hidden> wrote:
> Could you report the error you are seeing and a piece of code to reproduce
> your
> problem? It should work the same. For instance, is XFPNumber variable
> accessible
> from your constructor function?
>
>
> Yes, the message was:
>
> octave:1> l2r(0.4)
> error: `XFPNumber' undefined near line 7 column 9
> error: called from:
> error:   /usr/share/octave/3.2.4/m/left2right/l2r.m at line 7, column 7
[snip]
> ##XFPNumber =
> java_get('eu.simuline.arithmetics.left2right.XFPNumber','ONE');
> XFPNumber = java_invoke('eu.simuline.arithmetics.left2right.XFPNumber',
>                         'atomic',
>                          java_new('java.lang.Double',2.5));
>
> I thought, octaverc was invoked quite early.

The problem is that global variables are not visible within a function.
You should use the global keyword to make your function access
global XFPNumber.

> Note also that if you overload the + operator that way (assuming it
> works ok, I'm not 100% sure you can overload standar operators
> with dispatch), this will use your lr_plus function for *any* octave_java
> object.
>
>
> Yes, this is exactly the problem.
> I do not want this.
> I would like to dispatch separately for lr-arithmetics, interval
> arithmetics, bigdecimal arithmetics and all others.
>
> How can i do this?
> Can you tell me where to look up the class octave_java?

The "dispatch" method only works at octave level, for different type of
octave objects. From the octave point of view, *all* java objects are of
the same octave-internal type "octave_java". So the only thing that you
can do at octave-level is to dispatch the + operator for all java objects.

But nothing prevents you from using java polymorphism to continue
the dispatching at java-level.

Michael.