What is the largest number in lua?

totebo · May 2015

A 64 bit integer is 19 digits long, and used by Gamekit and Google Play as a max value for scores.

Is this supported by lua? If not, which is the largest number supported?

totebo · May 2015

My scores are coming out as 2,147,483,647, which most likely means that Gideros Lua doesn't support 64 bit integers. Bummer!

Interestingly I found in Lua 5.3 reference manual that it supports 64 bit integers.

Standard Lua uses 64-bit integers and double-precision (64-bit) floats, but you can also compile Lua so that it uses 32-bit integers and/or single-precision (32-bit) floats.

Which version of Lua does Gideros use? If not 5.3, could it be updated?

totebo · May 2015

Does anyone know which Lua version gideros uses?

ar2rsawseen · May 2015

I think it was 5.1, as stated in the repo:
https://github.com/gideros/gideros/tree/master/lua

but if you use luajit I think it might be different, might be even cpu specific

talis · May 2015

Ok not %100 sure but after writing

print(_VERSION)

in the main.lua it printed me:

Lua 5.1

So i guess 5.1 with the 2014.10 Gideros Studio. So just try with your Gideros version to find out the Lua version.

SinisterSoft · May 2015

LuaJIT can also be used, it has a different (wider?) range...

http://bitop.luajit.org/semantics.html

"Hexadecimal literals are treated as unsigned numbers by the Lua parser before converting them to the Lua number type. This means they can be out of the range of signed 32 bit integers if the Lua number type has a greater range. E.g. 0xffffffff has a value of 4294967295 in the default installation, but may be -1 on embedded systems."

hgy29 · May 2015

I guess that lua number would be 32 bits on 32 bits archs and 64 bits on 64 bits archs...

totebo · May 2015

Thanks guys.

The latest Gideros build, 2015.05.09, uses Lua 5.1. I can confirm Lua 5.1 does not support 64 bit integers. This means it can't take advantage of the 64 bit scoring system in Gamekit and Google Play.

@hgy29, I am testing this on an iOS 64 bit build, but Lua appears to restrict it to 32 bit.

Questions, questions:

1. Can Gideros be upgraded to use Lua 5.3? If so, is this something that would be considered by the Superhero Core Team?
1.1. If not, could the LNUM patch be applied to the current Gideros Lua 5.1? https://github.com/LuaDist/lualnum
1.2. If not, is there a neat workaround for this issue? One solution could be to rewrite, or extend, the Gamekit and Google Play services to work with strings as well as 32 bit integers.
2. LuaJIT. Will using it allow 64 bit integers?

Look forward to thoughts on this, especially from the Core Team.

Niclas

hgy29 · May 2015

We are thinking about moving to luajit, main concern being that lua files should not be exported in readable format and that parsing itself should be avoided in mobile platforms. When/if we do this I am pretty sure we will use the latest version available to us. @SinisterSoft is thinking about this move since some time now...

SinisterSoft · May 2015

LuaJIT appears to support a much larger range than standard Lua 5.1 (56 bit?)

x=0xffffffff
print(x)
x=x+0x10000000000
print(x)
x=x-0x10000000000
print(x)

results in:
main.lua is uploading.
Uploading finished.
4294967295
1103806595071
4294967295

Those numbers are large enough for a score for me.

I don't know what the support is though with regard to getting the >32 bit number out of Lua and into Google Play.

- Anthony

totebo · May 2015

@hgy29 okay, thanks for clarifying.

@SinisterSoft 13 digits, that's good!

The idea is sending a score that also contains data about the previous game session, so a separate database is not needed for that. I could then use that to show data from friends' scores effortlessly and cheaply. That's why I was hoping to use more than 10 digits. Greedy!

SinisterSoft · May 2015

It looks like it's accurate to 56 bits.

SinisterSoft · May 2015

You should use the lower bits for extra info if you are using facebook score - that way you can divide it and the scores still stay in order.

totebo · May 2015

Thanks Sinister. In the end I chose to modify gamekit.mm to accept strings, which works well in this case. For the save state to work I needed 18 digits in the end.

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