create struct array in oct-file

[John W. Eaton]

On 12-Jun-2010, Andy Buckle wrote:

| My (simplified) dysfunctional attempt is below. I am sure this is
| easy, but I can't figure it out.
| 
| #include "octave/oct.h"
| #include "octave/ov-struct.h"
| 
| DEFUN_DLD (create_struct_array, args, nargout,
|               "example of struct array") {
|       octave_value_list retval;
|       const int n=2;
|       int i;
|       Array2<Octave_map> aom(n,1);
|       for (i=0; i<n; i++) {
|               Octave_map om;
|               om.assign("a",i);
|               om.assign("b",i+1);
|               aom(i,1)=om;
|       }
|       retval(0)=Cell(aom);
|       return retval;
| }
| 
| This fails to compile, with:
| create_struct_array.cpp:16: error: call of overloaded
| ‘Cell(Array2<Octave_map>&)’ is ambiguous

Octave_map already is a struct array, so there is no need to put it
inside an Array2 object.  I think the following will do what you want:

  #include "octave/oct.h"
  #include "octave/oct-map.h"

  DEFUN_DLD (create_struct_array, , ,
    "example of struct array")
  {
    octave_idx_type n = 2;

    Cell avals (n, 1);
    Cell bvals (n, 1);

    for (octave_idx_type i = 0; i < n; i++)
      {
        avals(i) = i;
        bvals(i) = i+1;
      }

    Octave_map m;

    m.assign ("a", avals);
    m.assign ("b", bvals);

    return octave_value (m);
  }

jwe