Re: #matr~ vs ##matr (and: arity, questenian and !!)

[Loïc Grenié <loic.grenie@gmail.com>]

On Mon 27 Nov 2023 at 14:13, Bill said:

On Sun, Nov 26, 2023 at 07:48:32PM -0800, Ilya Zakharevich wrote:
> On Fri, Feb 05, 2021 at 05:54:48AM -0800, Ilya Zakharevich wrote:
> > On Fri, Feb 05, 2021 at 05:46:43AM -0800, Ilya Zakharevich wrote:
> > >   Is not it desirable to implement ##matr as an (optimized) synonym for #matr~?
> > >
> > > If the answer to the second question is positive, then one can maybe
> > > improve things by returning a special value (such as -1) for scalars…
> >
> > Well, to get things yet simpler, one can make ###x to return 0 for
> > scalars, 1 for vectors/lists and 2 for matrices.
>
> Taking all these things together, I think that in the best of the
> worlds one would have these:
>
>   #mattr~   optimized in the compiler to (an equivalent to) (matsize(mattr))[1]

This one will not break backward compatibility while being easy to do.

See the new branch bill-translength.

? M=matrix(200,201,i,j,random(2^200));
? for(i=1,1000,#M~)
  ***   last result computed in 0 ms.
instead of
  ***   last result: cpu time 485 ms, real time 486 ms.

     This one is really useful! I've never thought to ask...

     Thanks!

            Loïc