How to compute and execute the LUA code in a string in Lua _lua

A, Lua execution string

There is a problem during the run, I have a string, is a mathematical expression, how to calculate the value of this string expression?
For example, the local param = "7*100", I need the result is actually 700, but how to calculate this value directly? Methods are as follows

Prefix the string with a "return"
Then LoadString gets a function later.
Then perform a return value of 700, so that by converting, the results are as follows:

Second, the implementation of the LUA code as a string

Sometimes we want to be able to dynamically switch contexts in our code and change the process of processing the program, at which point we need to generate some code in accordance with our own will, at which point we need to execute some LUA code from the string

In our project I hope that I can get down from the server A can execute the LUA code, use this code to update the project resources, so as to avoid whether it is the first chicken or egg problem

Copy Code code as follows:

--defining a string to use as function later
Funcstr = "Print (' Test ')"
--running it directly
LoadString (FUNCSTR) ()
--defining a function from the string and running it
Func = LoadString (FUNCSTR)
Func ()