Template BigNum implemented without runtime loops

[Don Clugston]

BCS wrote:
> I have implemented a arbitrary precision integer type using a struct and 
> templates. Currently it supports ==, +, -, *, +=, -= and *=. It should 
> be fairly efficient as it uses static foreaches and asm blocks to unroll 
> all of the looping and conditionals.
> 
> I haven't tested the multiplication much yet so it may well contain 
> bugs. (If it doesn't I will be vary surprised)
> 
> On my system DMD crashes for size > 73 (e.i. 73 * 32b = 2336b).

Of course, there's not much value in unrolling loops to that extent 
(cache misses will cost you more than you'll gain by eliminating the 
last couple of branch instructions).

However, the use of tuples and static foreach to enforce asm unrolling 
is very cool. This ought to work with mixins as well as direct asm 
instructions. I'd never found a way of mixing in multiple blocks of code 
at the same level -- this technique will probably solve the problem.
(And it might be a way of doing very high performance expression 
templates :-)  ).