Lua error "attempt to perform arithmetic on a string value"

Question

I have this simple script in Lua:

local function addDigits(n)
 n=n..""
 local s1=0
 for i=1,n:len() do
 s1=s1+n:sub(i,i)
 end
 return s1
end

If I call it with small values, as

addDigits(12345678123456)

it performs well. But if I call it with larger values, as

addDigits(1234567812345678)

I receive "attempt to perform arithmetic on a string value".

I've tried with "toNumber",

s1=s1+tonumber(n:sub(i,i))

but I recieve "attempt to perform arithmetic on a nil value".

I am very new to Lua, so any help will be great! Thanks!

• David Crayford: See stackoverflow.com/questions/945731/…
• Uli Schlachter: Works fine here with Lua 5.3.3
• Adrian Kreator: I use Windows, and the latest version I found is Lua 5.1

Answer 1

The number 12345678123456 becomes 1.2345678123457e+015 when being converted to a string, so you have problem with s1=s1+".", s1=s1+"e" and s1=s1+"+".

• Adrian Kreator: I try to use this library here: oss.digirati.com.br/luabignum/bn, but I use the redis-cli, and I cannot use require. So, I just added BigNum.lua in my directory, but still I cannot use the library. Any suggestion?
• Egor Skriptunoff: "How to install Lua package in redis" is a separate question. Sorry, I know nothing about redis.