Negative zero??

[dingo]

Hello.. First post here.
I noticed an odd bug in luaplayer while working on my complex number calculator. Someone must have surely noticed this, but I've tried searching and I've not found anything.
According to Luaplayer, -1*0 = -0..
Here's the code I've tested it with:

Code: Select all

zero = 0*-1
screen:fillRect(0,0,480,272,Color.new(0,0,0))
screen:print(200,100,tostring(zero),Color.new(255,255,255))
screen:print(200,110,tostring(zero == 0), Color.new(255,255,255))

screen:flip()

while true do
	screen.waitVblankStart()
end

it outputs this:
-0
true

which I guess means -0 has a different value to 0, but is still equal to it.

I'm using user-mode lua (for 2.0 fw) and I've also tested it on the luaplayer for windows alpha.

[Jim]

Floating point numbers have both +0 and -0. It's mostly of use to people trying to perform analytical calculations. One example is it can be used to find out if a numerical series converges to 0 and if it approached from above (+0) or below (-0).

It's not a lua bug and you probably shouldn't need to worry about it.

Jim

[dingo]

Ooh OK, thanks for explaining that..