Re: making element_type NDArray parent classes of element_type Matrix

[John W. Eaton]

On 10/21/2014 07:00 PM, Carnë Draug wrote:
> Hi
>
> at the moment, both Matrix and NDArray classes are derived from
> Array<element_type>.  I may be missing something but I think it makes
> more sense to have the Matrix classes derive from a NDArray of the
> corresponding element_type.
>
> For starters, I did this for boolMatrix and boolNDArray [1]. It is
> building fine and make check is successful.  I would continue this but
> maybe others have different opinions on what things should derive
> from.
>
> There is also the case to have Matrix classes inherit from both an
> AbstractMatrix and element_type NDArray, but that may complicate
> things too much for very little gain (or any gain?).
>
> The specific thing that triggered this was trying to implement the
> bitpack and bitunpack as boolNDArray methods [2].  That's when I
> noticed that implementing on boolNDArray would not make it available
> for boolMatrix
>
> Could anyone comment on this change?  If we are going to change where
> things derive from, we may as well go for broke and make other bigger
> changes that may have been hold back to not break existing code.
>
> Carnë
>
> [1] https://bpaste.net/show/6b5a03b8bda3
> [2] http://lists.gnu.org/archive/html/octave-maintainers/2014-10/msg00053.html

I think this is a reasonable change.  At the same time, we should ensure 
that Matrix objects always have 2 dimensions.  For example, we currently 
have

  ComplexMatrix (const dim_vector& dv) : MArray<Complex> (dv.redim (2)) { }

in ComplexMatrix.h but not in the bool and char Matrix equivalents.  The 
purpose of the redim function is to smash all dimensions higher than 2 
into the second dimension.  For example if you used this constructor to 
create a ComplexMatrix with a dim_vector containing dimensions [2,3,4], 
you'd end up with a 2x12 matrix.  That makes sense given what typically 
happens with things like indexing (using rules we inherit for 
compatibility with Matlab).

jwe