0-extent matrices?

[Kurt Hornik]

>>>>> Thomas Lumley writes:

> Implementing 0-extent matrices turns out to be easy -- it's almost
> entirely a matter of removing the tests for 0.  There seems to be only one
> thing that may require special-case handling, but I'm not sure what the
> Right Thing to do is.

> If m is a 0x4 matrix, say, what should 2*m, 2+m and so on return?

> Since m+m is a 0x4 matrix but 2*as.vector(m) is NA we can't have complete
> consistency.  My preference is for these operations to happen elementwise
> -- ie m+m is a 0x4 matrix.  Comments?

Sounds very much like going the Octave/MATLAB way.  I thought we'd
eventually have a `Matrix' class for such things?

-k
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