Re: [ANN] Lua 5.3.0 (rc4) now available

[Paige DePol <lual@...>]

Tim Hill <drtimhill@gmail.com> wrote:

>> On Jan 12, 2015, at 2:08 PM, Coda Highland <chighland@gmail.com> wrote:
>> 
>> On Mon, Jan 12, 2015 at 2:04 PM, Michael Welsh Duggan <mwd@cert.org> wrote:
>>> Sean Conner <sean@conman.org> writes:
>>> 
>>> 
>>> 0x1000000000000
>>> 
>>> --
>>> Michael Welsh Duggan
>>> (mwd@cert.org)
>> 
>> 1 << 48.
>> 
>> We have bitops now. :P
>> 
>> /s/ Adam
> 
> However, as Lua does little (if any) constant folding at compile time, this will be more expensive than the equivalent hex/decimal literal.
> 
> —Tim

Lua does constant folding... grep the codebase for 'folding'! 

"a = 1 << 5"

Compiles to:

main <ackoop:0,0> (2 instructions at 0x7f8db8405270)
0+ params, 2 slots, 1 upvalue, 0 locals, 2 constants, 0 functions
	1	[2]	SETTABUP 	0 -1 -2	; _ENV "a" 32
	2	[2]	RETURN   	0 1
constants (2) for 0x7f8db8405270:
	1	"a"
	2	32
locals (0) for 0x7f8db8405270:
upvalues (1) for 0x7f8db8405270:
	0	_ENV	1	0

Looks like it folded "1 << 5" to "32" correctly! :)

~pmd