Re: tostring vs. nan, inf

[Jose Torre-Bueno <jtorrebueno@...>]

But I notice nan cannot be assigned to a variable, the variable is set to nil.

> c = nan
> =isnan(c)
false
> =c
nil

but a variable with nan as its value can set another variable to nan:

> a = 0/0
> = isnan(a)
true
> c = a
> = c
nan

further two variables set to nan are not equal to each other:
> a = 0/0
> b = 0/0
> = a==b
false

But nan is equal to itself:
> = nan == nan
true
> = nan
nil
> 



this says to me that nan is not a pseudo constant in the same way nil is.  I assume there is something subtle going on here.  Perhaps somebody can explain why this is so.


On Apr 10, 2012, at 5:38 AM, Luiz Henrique de Figueiredo wrote:

>> but I don't see how to detect nan portably.
> 
> function isnan(x) return x~=x end
> function isinf(x) return (x+1)==x end
> 
> See http://lua-users.org/lists/lua-l/2005-02/msg00758.html for alternatives
> and my lmathx for a C implementation:
> 	http://www.tecgraf.puc-rio.br/~lhf/ftp/lua/#lmathx
>