Biggest integer in Gideros 2015.12 Lua 5.1

totebo

I am looking to use the largest number available in Lua. I assumed this number would be 2,147,483,647 (signed 32 bit Int) or 4,294,967,295 (unsigned 32 bit Int). After a little testing it appears to be 99,999,999,999,999. It's a lot better of course, but can someone explain why this is the biggest number?

This is how I tested:

print(99999999999999) -- 99999999999999 print(99999999999999.1) -- 99999999999999 print(9999999999999.9) -- 9999999999999.9 print(100000000000000) -- 1e+14

antix

I think LUA uses a 53 bit number, so 2^53 would be the biggest integer you could have.

I also discovered recently that sometimes when doing math you can get the result -0.0 which causes lots of bother. In that case you can check vs the following... 2^-53

tkhnoman

It's actually not the biggest, 1e+14 is just because lua use rounding (it's not error, you can still process it)

You can always process the data like the old days, so if it exceed that 1e+14, simply put big numbers at another variable, and mod it.

hgy29

It is because Lua numbers are not ints, but double precision floats, with a 53 bits mantissa. https://en.m.wikipedia.org/wiki/Double-precision_floating-point_format

totebo

That's great information guys, thanks! So, which IS the largest number you can perform operations on!?

SinisterSoft

You mean the largest int ?

ar2rsawseen

https://www.wolframalpha.com/input/?i=2^52

totebo

Bingo! An answer veiled in mystery. Nice site @ar2.

Drumroll...

4,503,599,627,370,496

antix

So that's how many sprites you think you are going to have onscreen at once?

totebo

Yeah, should be cool, no?

hgy29

Actually the biggest integer you can store is 1.7976931348623157 × 10^308, since this was your original question, but the only operations you can do on it without losing information is dividing it by 2 or substracting another number with the same exponent...