Assign Cell to octave map: error

[John W. Eaton]

On 12-Mar-2009, alexander.rusakov at googlemail.com (Alexander Rusakov) wrote:

| Bug report for Octave 3.0.3 configured for i686-pc-linux-gnu
| 
| Description:
| -----------
| 
| I believe that I found a bug in Octave c++ API. The problem that it is not
| possible  to assign arbitrary cell to an octave_map because of error from
| octave API.  This happens if:
| 1) Octave_map already has got some data
| 2) The size of Cell != 1.
| 
| I guess that line 461 in oct_map.cc file contains a bug. Probably the whole
| function has got some bug because I can not understand why there is  a need
| of comparison of dimension of octave_map and Cell which is only an element
| in map.
| 
| 00448 Octave_map&
| 00449 Octave_map::assign (const std::string& k, const Cell& rhs)
| 00450 {
| 00451   if (nfields () == 0)
| 00452     {
| 00453       maybe_add_to_key_list (k);
| 00454
| 00455       map[k] = rhs;
| 00456
| 00457       dimensions = rhs.dims ();
| 00458     }
| 00459   else
| 00460     {
| 00461       if (dims () == rhs.dims ())
| 00462         {
| 00463           maybe_add_to_key_list (k);
| 00464
| 00465           map[k] = rhs;
| 00466         }
| 00467       else
| 00468         error ("invalid structure assignment");
| 00469     }
| 00470
| 
| 
| Repeat-By:
| ---------
| 
| My problem that this code does not work:
| 
|  //This does not work as I expect
|  Octave_map omap;
|  cout << " Adding cell arrays to one maps \n";
| {
|   // I am trying to create 1d cell array of size 1
|    dim_vector dv(1);
|    Cell oc(dv);
|    cout << "Trying to add cell array of size " << dv(0) << " is added to
| octave_map" << endl;
|    omap.assign("cell1", oc);
|    cout << "cell array of size " << dv(0) << " is added to octave_map" <<
| endl;
|  }
| 
|  {
|   // I am trying to create 1d cell array of size 2
|   dim_vector dv(1);
|   dv(0) = 2;
|   Cell oc(dv);
|   cout << "Trying to add cell array of size " << dv(0) << " is added to
| octave_map" << endl;
|  / /Here I get an error message  "error: invalid structure assignment"
|   omap.assign("cell2", oc);
|   cout << "cell array of size " << dv(0) << " is added to octave_map" <<
| endl;
|  }
| 
| So the produced output is :
| 
| Trying to add cell array of size 1 is added to octave_map
| cell array of size 1 is added to octave_map
| Trying to add cell array of size 2 is added to octave_map
| error: invalid structure assignment             <-------------------
| Octave message
| cell array of size 2 is added to octave_map
| 
| 
| I am also sending a simple example which demonstrates the problem, and when
| it happens. To compile:
| 
| mkoctfile TestOctaveCellMap.cpp
| To execute:
| octave --eval "TestOctaveCellMap"
| 
| 
| 
| Fix:
| ---
| 
|  I guess that assertion in oct_map.cc on line 461 must be removed. Probably
| extra changes are required.

No, I think it is correct.

An Octave_map is a wrapper for a std::map<std::string, Cell> object.
Each map key accesses a Cell object.  The dimension of the structure
array is the dimension of the Cell objects in the map.  The Octave_map
object ensures that all the Cells in the struct have the same size.

If you want to insert a Cell array into a 1x1 Octave_map object, then
you have to do something like

   dim_vector dv (1);
   dv(0) = 2;
   Cell oc (dv);
   omap.assign ("cell3", Cell (octave_value (oc)));

I suggest you make this change to your test function and return omap
from it so you can examine how Octave sees the structure you've
created.

jwe