Re: At the edge of LNUM patch

[Asko Kauppi <askok@...>]

Mark Hamburg kirjoitti 25.3.2008 kello 18:36:
> The patch should kick out of the integer realm at the boundary of
> floating-point precision not at the boundary of integer precision.  
> Thus,
> calculating 2 ^ 63 should result in the value being stored as a  
> double even
> though it could fit into a 64-bit integer.

But this is exactly what it does. The "integer realm" is signed  
integers, -2^63 .. +2^63-1 with int64 mode. 2^63 does not fit into a  
signed 64-bit integer.

One minor note for people who may feel threatened by this patch; with  
default (double + int32) setup, FP accuracy exceeds integer accuracy  
and any behaviour is exactly like it's been on unpatched Lua.

> This still gets you a lot more integer precision than a lot of code  
> is used
> to working with since 32-bit integers are more or less the norm.

Yes. Despite using signed range, one can actually store full hex 64- 
bit values (0..0xffffffffffffffff) in 64-bit mode. As long as no  
arithmetics happen on these values, and output is done using  
string.format('%x').

> If one were to make this change, then I think it would achieve the  
> property
> that Lua's execution would be indistinguishable whether the patch was
> installed or not which I think would be a good thing.

Maybe it's been this way all along?

-asko

> Mark