From: Adam Berent <adminIDEVELOPERONLINE.COM>

> I have looked at the gnu math libraries and frankly they
> make me want to blow my brains out. There are about a
> hundred source files. I don't even know where too start.

> However I would like to know what the trick is.
> Some people suggested storing the numbers in a string.
> This seems a bit crude and would probably be too slow.

Slow educational code can be found at
    http://www.notatla.demon.co.uk/CRYPTO/FBN_funcs.c
but for real use something such as already suggested should be used.
I was originally planning (because of the difficulty of picking the right
bits of large libraries) to use this but beside the performance there's
a bug affecting the top bit of 1024-bit numbers.

This is really an implementation in unsigned characters of pen and paper
arithmetic with (where there is some choice) simpler functions being
defined in ways that allow them to be used to build the more complicated
ones.

Some of the least readable code is OO and allows arbitrary integer sizes
unlike the fixed length of my example. Production code uses integers
rather than characters because they are a wider data type. Also mathematical
results involving speed become important and there are architectural issues
such as (quoting EAY)

: Normally I put in differnt version of the
: same code which helps differnt CPU/compiler combinations. Sparcs like
: *(a++), x86/gcc likes a[i], a[i+1], a[i+2], a[i+3], i+=4.

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