source3/lua-5.1.4/test/readonly.lua

   1 -- make global variables readonly
   2
   3 local f=function (t,i) error("cannot redefine global variable `"..i.."'",2) end
   4 local g={}
   5 local G=getfenv()
   6 setmetatable(g,{__index=G,__newindex=f})
   7 setfenv(1,g)
   8
   9 -- an example
  10 rawset(g,"x",3)
  11 x=2
  12 y=1     -- cannot redefine `y'