The same reason why we have : in the first place.
Taking self twice might be complicated if the variable not on stack.
Picture this:
a.b.c.d.foo(a.b.c.d, ...)
you have to get the value d twice, when colon operator copies the left value to the stack again
Lua is a small language with a lot of power, and the main reason for it is that it has not included the many 100s of proposals like this that have passed by in the last 20+ years.
In this case a little helper function can get rid of most of the inconvenience. If the overhead bugs you then introduce a local variable that you assign the value of "a.b.c.d" in your example.
local function dcall(ob, method, ...)
return ob[method](ob, ...)
end
local tweedledee = {name = "tweedledee"}
function tweedledee:hello()
print("hello",
self.name)
end
local box = { thing = tweedledee }
local method = 'hello'
dcall(box.thing, method)
