From: ptkwt@...1.aracnet.com (Phil Tomson)
Date: 2002-06-14T14:07:19+09:00
Subject: SWIG: returning a bool reference or pointer to Ruby

I've got a class that defines the following method:

class AEdge {
....

    virtual bool intersect( bool & overlap,
			    xyT & ix,
			    xyT & iy,
			    xyT & iix,
			    xyT & iiy,
    			    const AEdge & ae );
....
}; //AEdge.h

Where overlap,ix,iy,iix and iiy are really values that should be returned
by the function.  So in Ruby I'd like to be able to do:

intersection,overlap,ix,iy,iix,iiy = e.intersect(e1)
(where intersection is the true/false value which is the bool returned
from intersect).


I tried to do the following in the .i file to no avail:

%module Shapes
%include "typemaps.i"
bool AEdge::intersect(bool &OUTPUT,xyT &OUTPUT,xyT &OUTPUT,
xyT &OUTPUT,xyT &OUTPUT,AEdge&);
....

It kind of seems to me that I'm expecting a bit too much magic here but
that's similar to what was shown in the latest SWIG/Ruby doc.

I also tried:

%module Shapes
%include "typemaps.i"
%apply bool *OUTPUT { bool* overlap };
%apply int  *OUTPUT { xyT* ix, xyT* iy, xyT* iix, xyT* iiy };

but that didn't work either (NOTE: I tried both references and pointers
thinking that SWIG converts references to pointers so maybe I need to do
that too).

Can someone clarify how this is supposed to work?

BTW: I checked the typemaps.i file for Ruby and found no mappings from 
bool* to Ruby's TrueClass or FalseClass, so maybe that's the problem, but 
I'm not sure how to achieve this mapping.  I suspect this would be a lot 
easier if Ruby had a Bool type that could be either true or false.  I 
think it's been mentioned before, but it does seem a bit awkward that a 
variable set to true is of type TrueClass and a variable set to false is 
of FalseClass.

So how would one go about mapping from a bool on the C side to either a 
true or false on the Ruby side and visa-versa?

Phil