David Bateman wrote:
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
Thanks for pointing me in the right direction. That example gave me
exactly what I needed. I did find, however, that for simple comparison
operations, there are macros to make it *really* easy. The DEFBINOP_OP
macro allows you to simply implements an accesor function in the
user-defined type to return some integer value that can then be compared
against other octave types. In my case, I have a octave_socket class.
I used the DEFBINOP_OP macro as follow:
DEFBINOP_OP (lt, scalar, scalar, <)
DEFBINOP_OP (le, scalar, scalar, <=)
DEFBINOP_OP (eq, scalar, scalar, ==)
DEFBINOP_OP (ge, scalar, scalar, >=)
DEFBINOP_OP (gt, scalar, scalar, >)
DEFBINOP_OP (ne, scalar, scalar, !=)
I then had to overload the scalar_value() method in my user-defined type
and now I can compare against integers with all the operators.
Thanks again!
- John Swensen