Re: Explanation of Octave operator overloading

[David Bateman]

John Swensen wrote:
> Could someone give a quick tutorial on how the operator overloads work
> in Octave (and maybe add it as a section in the Da Coda Al Fine section
> of the wiki)?
>
> For example, I have defined a new type that derives from
> octave_base_value called octave_socket.  The problem is that I want to
> be able to compare it to numerical values.  I have already tried simply
> overloading the operator< to compare against octave_value.int_value() as
> well as just a plain int. 
>
> I see there are a bunch of macros called OCTAVE_INSTALL_*_*_*_CMP_OPS
> and assume I have to do something with these, but haven't been able to
> figure out what.
>
> Thanks.
>
> John Swensen
>
>   
A good little example is in 
octave-forge/extra/linear-algebra/ov-re-tri.cc which overloads the 
assign, ldiv, hermitian and transpose operators for a triangular matrix 
type. The reason its good is that it is tiny. In particular check the 
install_tri_ops functions, the functions that are defined immediately 
above this for the overloaded functions, and finally note that 
install_tri_ops is called immediately after the type is registered in 
the replacement chol.cc function. Note that I intend to delete this code 
in octave-forge now that the code to treat positive definite matrices is 
in octave itself, so rescuing it and using it as an example in da coda 
or del segna is probably a good idea. In fact if you are really 
motivated, rescuing both da coda and del segna, and this code and 
writing a chapter on oct-files for the octave 3.0 manual might be even 
better :-)

Regards
David