Converting calculation string to int in Lua

Question

I'm trying to get a string with multiple numbers to a single int like this:

x="5+5"  --amount of numbers is not constant
y=tonumber(x)
print(y) 

The result of this is nil while it should be 10 (int). The only way I could solve this is by first searching all the "+" and "-" with string.find() then cutting it to all the necessary parts and from there just tonumber(). It feels stupid to code at least a hundred rows of code for such a simple problem.

Answer 1

tonumber can be used only on a string that is a real number, not an arithmetic expression.

You can load the string and run it:

x = "5 + 5"
func = assert(load("return " .. x))
y = func()
print(y)

In Lua 5.1, use loadstring instead of load.