Arithmetic metamethods

The arithmetic metamethods are listed here:

• __add is called for the + operator
• __sub is called for the - operator
• __mul is called for the * operator
• __div is called for the / operator
• __pow is called for the ^ operator
• __mod is called for the % operator
• __unm is called for negation (for example y = -x)

Example

mt={}
mt["__add"] = function(a,b)
if type(b) == "string" then
a[#a+1] = b
elseif getmetatable(a) == getmetatable(b) then
for k,v in pairs(b) do
a[#a+1] = v
end
else
error("Invalid datatype for + operator!",0)
end
return a

end

t={}
setmetatable(t,mt);

-- Now	use + to call the __add metamethod of the table t
t1	= t	+	"foo"	-->	t[1]	= "foo"
t1	= t	+	"bar"	-->	t[2]	= "bar"