Hpw make lists that are easy to sort.

[Anton Vredegoor]

Paul Rubin wrote:

> Well there are various hacks one can think of, but is there an actual
> application you have in mind?

Suppose both input lists are sorted. Then the product list is still not 
  sorted but it's also not completely unsorted. How can I sort the 
product? I want to know if it is necessary to compute the complete 
product list first in order to sort it. Is it possible to generate the 
items in sorted order using only a small stack?

Also, I have a sumfour script that is slow because of sorting. It would 
become competitive to the hashing solution if the sorting would be about 
ten times faster. If the items could be generated directly in order the 
script would also have only a very small memory footprint.

> If you really want the sum of several probability distriutions (in
> this case it's the sum of several copies of the uniform distribution),
> it's the convolution of the distributions being summed.  You can do
> that with the fast fourier transform much more efficiently than
> grinding out that cartesian product.  But I don't know if that's
> anything like what you're trying to do.

I want the product, but sorted in less time. If Fourier transforms can 
help, I want them :-)

A.