proposal for changing Array interface

[John W. Eaton]

On 21-Jan-2010, Jaroslav Hajek wrote:

| after some more thinking about the problems, I propose the following:
| 
| 1. Remove the Array<T>::Array (octave_idx_type) and Array<T>::Array
| (octave_idx_type, const T&) constructors.
| 2. Remove the dim_vector::dim_vector (octave_idx_type) constructor.
| 3. Rename Array<T>::resize (octave_idx_type) and resize
| (octave_idx_type, const T&) to resize_1d.
| 
| Rationale:
| 1. Each Array has always at least 2 dimensions, so these would-be 1D
| constructors are in fact 2D, only n is promoted to n, 1. It's not
| particularly clear.
| 1a. The second constructor in 1 prevents a clean definition of a 2D
| constructor Array (octave_idx_type, octave_idx_type), because of the
| conflict for T = octave_idx_type.
| 2. like 1. dim_vector (octave_idx_type) bites.
| 3. Similar to 1a, this prevents a clean definition of 2d resize (which
| is more useful imho). Besides, contrary to intuition, resize (n) does
| *not* behave like resize (n, 1) but rather like resize (1, n) and
| fails for actual nonempty 2D arrays - it mainly exists to handle
| out-of-bounds linear assignments. I would prefer to hide this method
| as it is inconsistent with all the rest.
| 
| With these changes, it should be possible to cleanly remove the
| MArray2 and MArrayN classes and make all Matrix, Vector and NDArray
| classes inherit from MArray, which should facilitate simpler
| conversions and reduce code duplication.
| 
| These changes will obviously break compatibility.
| comments?

I favor cleaner design over backward compatibility.  From your
description, these changes seem OK to me.  I agree that having the
single argument constructors create 2D arrays is confusing.  It wasn't
always this way.  They used to generate 1D arrays.  That could be
useful for a general purpose array class, but for Octave, we then had
to ensure that all arrays we created actually had two dimensions.  So
it seemed to make sense to enforce that in the Array class.  But it is
probably better to just require a minimum of 2 dimensions when
constructing the arrays.

jwe