why did I get a decimal point by using loadstring in Lua

Question

I have a scenario that I need pass dynamic operators into loadstring. This is where I found it and I don't understand.

Please see the following output:

> a = '3'
> b = '7'
> operator = '+'
> loadstring("return a" .. operator .. "b")()
10.0 -- Why do I get then with a decimal point.
> loadstring("return 3" .. operator .. 7)()
10   -- But this one is not?

Can anyone explain what's going on inside loadstring since I thought I should get the same result?

Answer 1

The manual says this about arithmetic operators applied to strings:

if both operands are numbers or strings that can be converted to numbers (see §3.4.3), then they are converted to floats

Perhaps you want

loadstring("return " .. a .. operator .. b)()

instead of

loadstring("return a" .. operator .. "b")()