8.8 Modules

Here we explain one possible way to simulate modules in Lua. The main idea is to use a table to store the module functions.

A module should be written as a separate chunk, starting with:

if modulename then return end  -- avoid loading twice the same module
modulename = {}  -- create a table to represent the module

function modulename.foo (...)
  ...
end

Any code that needs this module has only to execute dofile("filename") , where filename is the file where the module is written. After this, any function can be called with

modulename.foo(...)

If a module function is going to be used many times, the program can give a local name to it. Because functions are values, it is enough to write

localname = modulename.foo

function open (mod)
  local n, f = next(mod, nil)
  while n do
    setglobal(n, f)
    n, f = next(mod, n)
  end
end