  lua-l archive

• Subject: Re: Numeric key collision related bug in Lua 5.3
• From: Tim Hill <drtimhill@...>
• Date: Wed, 22 Apr 2015 12:12:18 -0700

```> On Apr 22, 2015, at 9:13 AM, Roberto Ierusalimschy <roberto@inf.puc-rio.br> wrote:
>
>
> My guess is that the best sollution would be to change the definition
> of equality (to a simpler one :-). Two numbers should be considered
> equal if they represent the same mathematic value; period. (In terms
> of implementation, it means that integer-float should be compared
> converting the float to an integer; if the conversion fails, the numbers
> cannot be equal.) That definition is simple, sounds sensible and
> easy to explain, and makes equality transitive.
>
> -- Roberto
>

+1, for all the reasons you state.

What about relational operators? Consider this:

a = (1<<60) + 180
b = (1<<60) + 200
bf = b + 0.0
print(a < b)					-> true
print(a < bf)					-> false (!)
printf(a < math.tointeger(bf))		-> true

Of course, I carefully chose those numbers, but the truncating effect of integer->float will give strange results when doing (say) table.sort() on mixes of floats and integers.

—Tim

```