Calling Lua functions

The Lua hello function we used in the previous section is a good example to demonstrate global variables, but it is not how you would usually implement such a feature. Now consider a more suitable implementation:

function greetings(whom)
    return "Hello " .. whom
end

This Lua greetings function expects whom as a function parameter and returns the greeting string instead of printing it out. You can use the greeting string in more flexible ways, for example, by using it on a GUI window.

Earlier in this chapter, while learning how to execute Lua scripts, we implemented the execute function in our executor. We can invoke greetings with it:

LuaExecutor lua;
lua.executeFile("script.lua");
lua.execute("greetings('Lua')");

But this is not C++ calling a Lua function; it is a Lua script calling a Lua function. C++ just compiles the Lua script and has no access to the function’s return value...