Re: newbie question on using octave structures in external C++ functions

[David Bateman]

Jim H wrote:
> Hi,
> I would like to know how to determine the data type of a field in an octave
> data structure passed to a c++ function.  The manual and wiki provide some
> good examples, but my problem is to pass in a structure and assign values to
> c++ variables used by the external function.  To assign those values, it
> seems I need to know if the field is an integer, string, etc.  Here's a
> brief example where I could use some help.
> 
> #include <octave/oct.h>
> #include <octave/ov-struct.h>
> int aval;
> DEFUN_DLD(shombs_defs,args, , "show mbs defaults")
> {
>   int nargin = args.length ();
>   octave_value_list retval;
> 
>   if (nargin != 2)
>     print_usage ();
>   else
>     {
>       Octave_map arg0 = args(0).map_value ();
>       std::string arg1 = args(1).string_value ();
>               for (Octave_map::iterator p0 = arg0.begin() ; 
>                     p0 != arg0.end(); p0++ )  {
>                      // print keys and values
>                      std::cout << " key =>" << arg0.key( p0 ) << std::endl;
>                     octave_value( arg0.contents( p0 ) ).print( std::cout ,
> false );
>                     // how do I do the following?
>                     if ( arg0.key(p0) IS "foo" AND arg0.contents(p0)  IS
> INTEGER ) {
>                           aval = arg0.contents(p0);
>                     }
> ...
> 
> Thanks in advance for hints on this, and if there is good place to read
> about c++-callable methods that apply to structures, please direct me there.
> 
> Jim
> 


The 2.9.14 version of the manual has a full example of what you want.
See the file

http://velveeta.che.wisc.edu/cgi-bin/cvsweb.cgi/octave/examples/structdemo.cc?rev=HEAD

D.