lua-users home
lua-l archive

[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index] [Thread Index]

On 6/26/16, Sean Conner <> wrote:
>   First off, a 64-bit integer can store values in two ranges:
> 	-9223372036854775808 ..  9223372036854775807
> 	                   0 .. 18446744073709551615
> A double can "safely" store integers in the range:
> 	   -9007199254740992 ..     9007199254740992
> I say "safely" because past that range, integers start having "gaps"
> between [...]

I'm well aware of the fact that typically only integers less than 2^53
can be "safely" stored in Lua numbers (prior to Lua 5.2), and I'm fine
with this.

> The safest course is to check that the result (as a double) fits in the
> "safe" range and if not,

While this was not at all my original concern, you helped me to decide
that I should have a function dedicated to getting huge integers from
the Lua stack. BTW, do you know of a simple way of checking that a
floating number is in the safe integer range? I see that Lua 5.2's
implementation of file:seek does some range checking but it only
detects a number being outside, say, the 64 bits, not out the "safe"
53 bits.