Detect negative zero (was Re: Infinity as index)

["Liam Devine" <liamdevine@...>]

On 24/04/14 17:15, Dirk Laurie wrote:
> 
> The hardest test of all is to distinguish between 0 and -0.
> If you can improve on the following, please post.
> 
> if x==0 and 1/x>0 then -- x is 0
> if x==0 and 1/x<0 then -- x is -0
> 
binary32 small endian

$lua53 -e"local a = -0. print( (function(x) return x == 0 and
tostring(x):byte(1) == 45 end)(a))"
true
$ lua53 -e"local a = 0. print( (function(x) return x == 0 and
tostring(x):byte(1) == 45 end)(a))"
false

-- 
Liam

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