1. Posted by erdem on Fri, 18 Feb 2011 08:16:07

    Hi there is an example in Chapter 4 Defining Basic Arithmetic Using ... subtitle.

     tbl1 = {"alpha", "beta", "gamma"}
 tbl2 = {"delta", "epsilon", "zeta"}
 tbl3 = {}
 mt = {}

 setmetatable(tbl1, mt)
 setmetatable(tbl2, mt)
 setmetatable(tbl3, mt)

 function mt.___add(a,b)
 local result = setmetatable({}, mt)
 -- Copy table a in first
 for i = 1, #a do
 table.insert(result, a[i])
 end
 -- Copy table b in second
 for i = 1, #b do
 table.insert(result, b[i])
 end
 return result
 end

 add_test = tbl1 + tbl2

    When i try to compile this example i get an error message like this:

    lua -e "io.stdout:setvbuf 'no'" "metatable.lua" lua: deneme.lua:23: attempt to perform arithmetic on global 'tbl1' (a table value) stack traceback: metatable.lua:23: in main chunk [C]: ? Exit code: 1

    Thanks. Very nice book. I wish you continued success.

  2. Posted by jnwhiteh on Fri, 18 Feb 2011 20:42:24

    You have three underscores on ___add, and you only need two, i.e. __add.

  3. Posted by erdem on Fri, 18 Feb 2011 23:09:49

    Thank you very much :)