memoization in Ada? Hash ADT?

[Kenneth Wolcott <kennethwolcott@gmail.com>]

Hi;

  I'm working on the Rosetta Code task:

"Stirling numbers of the second kind"

I have a working recursive solution written in Ada but I'd like to memoize it to cut down on the redundant and duplicative calls (similar to a recursive solution to calculating the Fibonacci sequence).

So I think I need a hash ADT (which I've used in Perl) but I've never used in Ada.

So I want to preserve the calculation of the Stirling2 for each N and K so I can do a lookup.  If this were based on a single unsigned integer, an array would suffice.  Maybe a 2d array would suffice?

Thanks,
Ken Wolcott