[Numpy-discussion] A new matrix class

[Keith Goodman]

On Sun, May 11, 2008 at 12:44 PM, Charles R Harris
<charlesr.harris at gmail.com> wrote:
> On Sun, May 11, 2008 at 1:01 PM, Keith Goodman <kwgoodman at gmail.com> wrote:
>>
>> The most basic, and the most contentious, design decision of a new
>> matrix class is matrix indexing. There seems to be two camps:
>>
>> 1. The matrix class should be more like the array class. In particular
>> x[0,:] should return a 1d array or a 1d array like object that
>> contains the orientation (row or column) as an attribute and x[0]
>> should return a 1d array. (Is x.sum(1) also a 1d array like object?)
>>
>> 2. A matrix is a matrix: all operations on a matrix, including
>> indexing, should return a matrix or a scalar.
>>
>> Does that describe the two approaches to matrix indexing? Are there
>> other approaches?
>> _________
>
> Pretty well, I think. The thing about 2) is that ndarray routines break if
> they can't treat arrays as nested sequences, i.e. scalar indexing needs to
> return an array of one less dimension. So the matrix class shouldn't
> subclass ndarray in that case, but rather should use an ndarray as a
> component. More code to write, but such is life.
>
> 3) Everything is an array. I think Matlab treats scalars as 1x1 arrays.

So #3 is behave in a similar way to octave/matlab?  In octave/matlab
1x1 matrices are handled in special ways, e.g. (nxm) * (1x1) is
allowed. From the perspective of the user a 1x1 matrix is a scalar.