Re: Very big Integers

["Vincent P. Amiot" <godzilla@mozilla.com>]

Some 8 years ago I implemented an embryo of RSA that needed big numbers and
a "modular exponentiation" (you have to perform modulus op on the
exponentiation as you go to prevent you from having to deal with
untractably large numbers).

At the time I used limited private taht were bit arrays in little endian
configuration, so the INT was actually:

	type Int is array (0..Size-1) of Boolean;
	pragma Pack (Int);  

where Size could be a generic formal parameter or a constant.

Besides the 4 basic binary ops (+,-,*,/), the unary ops (+,-), the
comparisons, you will need another basic operation: the numeric litteral...

It can be elegantly provided as:

	function "+" (Left: String) return Int;

to be used as follows:

	X : Int := +"12345678901234567890";

(of course raise constraint error if somebody tries to feed in a string
that contains non-numerical chars...)

Hope this helps
Get back to me if you need further help
Vincent Amiot
Principal Consultant / Aonix  

Denny <vrandezo@trick.informatik.uni-stuttgart.de> wrote in article
<Pine.GSO.4.10.9904231559080.7427-100000@tick.informatik.uni-stuttgart.de>..