Re: Improved triu.m and tril.m

[Marco Caliari]

> using cellslices + vertcat + reshape is faster still:
>
>  m = min (nc, nr+k);
>  ii = max (1, (1:m) - k);
>
>  sl(2,:) = cellslices (x(:), ii, nr*ones (1, m));
>  sl(1,:) = cellslices (zeros (nr, 1), ones (1, m), ii - 1);
>
>  retval = reshape (vertcat (sl{:}), nr, nc);

Great, even if, it does not work for me... I think the problem is related 
to what I get with 3.2.3

octave:1> cellslices([1,2],1,0)
error: subscript indices must be either positive integers or logicals.

Maybe the result should be

{
  [1,1] = [](1x0)
}

Also this appears strange to me

octave:1> cellslices([1,2,3],[2,3],[1,1])
error: invalid range used as index.

> Out of interest, do you depend on triu/tril efficiency in an application?

Not really. I had a code with fft and matrix manipulations and it was 
slower in Octave than in Matlab just because of a final triu.

Cheers,

Marco