octave-3.6.2 vs octave-4.0.0-rc0: sparsersb.oct: derived class of octave_sparse_matrix in octave_value_list "ignored"ppspfpspf>

[Michele Martone]

Hi Octave Maintainers.

My `sparsersb' package [s] used to build/work under Octave, e.g. 3.6.2.
I gave a try to octave-4.0.0-rc4.

The `sparsersb' keyword continues returning a octave_value_list object having
been append()'ed (in position 0) to `retval'.
  "class octave_sparsersb_mtx : public octave_sparse_matrix"

In turns out that under octave-3.6.2 what sparsersb() returns is
being interpreted correctly (as octave_sparsersb_mtx).

What is being returned by octave-4.0.0-rc4 is wrong: it appears
as "Compressed Column Sparse" once it is being printed out.
This, rather than "Recursive Sparse Blocks".

So it's like something wrong in the innheritance mechanism.

Can anybody point out what changed from octave-3.6.2 to 
octave-4.0.0 w.r.t. this problem and how to correct in
sparsersb.cc ? 

 [s] 
svn+ssh://address@hidden/p/octave/code/trunk/octave-forge/main/sparsersb/src