> but you do not normally write a 4 function calculator because you > need one, you do it as an exercise in learning the language, as it > touches several areas and is easy to test. There is also a learning opportunity in the other direction: using metatables to generate code or parse trees. See these messages: http://lua-users.org/lists/lua-l/2017-02/msg00139.html http://lua-users.org/lists/lua-l/2011-03/msg01059.html