Re: Some thoughts on integer exponentiation (and an implementation)

[Oliver Kroth <oliver.kroth@...>]

>    I'm still confused.  Ignoring rotates (which rotate the bits) CPUs tend to
> support two forms of shifting, an unsigned variant (where 0 is copied in for
> right shifts) and a signed variant (where the sign bit is copied for right
> shifts) and are (nominally) used for multiplication/division by 2, which
> makes it an arithmetic operation, and which I use to replace certain
> exponential operations I used from Lua 5.1/5.2:
>
> 	x = 2^30	-- Lua 5.1, 5.2 to get 1073741824
>
> 	x = 1<<30	-- Lua 5.3 to get 1073741824
>
>    -spc
the difference in unsigned and signed shifting exists only in 
right-shifts, where the sign bit, which is at the leftmost position, is 
either kept (signed) or filled with zero or carry bit (unsigned)
On left-shifts no two versions are needed.

--
Oliver