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

[David Bateman]

Jim H wrote:
> David Bateman-3 wrote:
>   
>> 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.
>>
>> _______________________________________________
>> Help-octave mailing list
>> address@hidden
>> https://www.cae.wisc.edu/mailman/listinfo/help-octave
>>
>>
>>     
>
> Thanks for the reply, but I guess I was not clear.  I had read the fine
> manual and even better cookbook by Paul Thomas on the wiki, but their
> examples describe how to set a variable in the octave space, while I would
> like to learn how to determine a structure field's datatype in order to set
> a variable in the C++ space.  I'd iike to do something like:
>
> // c++ code
> int bob;
> bob=arg0(p0).contents();    // or something similar, assuming "contents" is
> an integer
>
> -Jim
>   
         
           int bob = arg0.contents(p0)(0).int_value();

D.



-- 
David Bateman                                address@hidden
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