user-defined Octave C++ functions

[owinebar]

  Hi.  I want to write a dynamically linked function for loading audio
file, using an external library like libsnd, returning a structure with
the format and relevant information.

   I've had problems creating such structures, though I think it may be my
lack of familiarity causing it.

For example,
#include <stdio.h>
#include <sndfile.h>
#include <octave/oct.h>
#include <octave/ov-struct.h>
#include <octave/oct-map.h>
#include <string>

DEFUN_DLD (test_struct, args, ,"test_struct")
{
  ColumnVector in (args(0).vector_value());
  Octave_map table ();
  octave_struct test;
  std::string field_name ("strfield");
  octave_value tstr ("test this");
  ColumnVector tmat (3);
  int i = 0;
  for (i=0;i<3;i++)
    {
      tmat(i) = i;
    }
  table[field_name] = tstr;
  field_name = string("matfield");
  table[field_name] = octave_value(tmat);
  
  test = octave_struct(table);

  return test;
}


gives the following errors:
address@hidden examples]$ mkoctfile test.cc
test.cc: In function `class octave_value_list Ftest_struct(const class
octave_value_list &, int)':
test.cc:21: no match for `Octave_map ()()[string &]'
test.cc:23: no match for `Octave_map ()()[string &]'
test.cc:25: no match for `octave_struct & = octave_struct *'
/usr/local/include/octave-2.1.31/octave/ov-struct.h:99: candidates are:
octave_struct::operator =(const octave_struct &)

whereas just changing the Octave_map to a *Octave_map, i.e.
#include <stdio.h>
#include <sndfile.h>
#include <octave/oct.h>
#include <octave/ov-struct.h>
#include <octave/oct-map.h>
#include <string>

DEFUN_DLD (test_struct, args, ,"test_struct")
{
  ColumnVector in (args(0).vector_value());
  Octave_map *table = new Octave_map();
  octave_struct test;
  std::string field_name ("strfield");
  octave_value tstr ("test this");
  ColumnVector tmat (3);
  int i = 0;
  for (i=0;i<3;i++)
    {
      tmat(i) = i;
    }
  (*table)[field_name] = tstr;
  field_name = string("matfield");
  (*table)[field_name] = new octave_value(tmat);
  
  test = octave_struct(*table);

  return test;
}

compiles without complaints.

What's up with that?  What's this Octave_map()() gcc was complaining
about?  And will my non-complaining version have memory leaking problems?

Lynn




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