Re: n-dim matrices

Christian Soeller wrote:
> Jeremy Howard wrote:
>
> > 14,17;...20,29). What if we created a new operator ';' that works within
a
> > list that creates a cartesian product?:
> >
> >   (10:20:2; 11:30:3);   # Cartesian product of 10:20:2 and 11:30:3 as a
LOL
>
> A possible approach. Two issues: (1) others might argue that we should
> use a multiplication like operator, e.g. x. Call it a separator and no
> such discussion would arise.

It would be nice to think Perl people were more open-minded ;-)

Making the result of ';' a real data structure would mean you could create
n-dim slices once and re-use them later. It also unifies the notations quite
nicely.

> (2) lazy evaluation is again critical: we
> don't want (10:100000; 0:1000) create a huge list in memory. So now we
> have a lazy list made up of two other lazy lists. Possible I guess.
>
It sure is. My list generation RFC already specifies this:

<quote>
=head1 ABSTRACT

This RFC proposes that the existing C<..> operator produce a lazily
evaluated list. In addition, a new operation C<:> is proposed that allows
for the generation of lazily evaluated lists based on any Perl expression.
</quote>

This would be a natural place to add ';' as part of the lazy list generation
tool-box.