How to 'unpack' table into function arguments

Question

I'm trying to call a function in Lua that accepts multiple 'number' arguments

function addShape(x1, y1, x2, y2 ... xn, yn)

and I have a table of values which I'd like to pass as arguments

values = {1, 1, 2, 2, 3, 3}

Is it possible to dynamically 'unpack' (I'm not sure if this is the right term) these values in the function call? Something like..

object:addShape(table.unpack(values))

Equivalent to calling:

object:addShape(1, 1, 2, 2, 3, 3)

Apologies if this is a totally obvious Lua question, but I can't for the life of me find anything on the topic.

---

UPDATE

unpack(values) doesn't work either (delving into the method addShape(...) and checking the type of the value passed reveals that unpackis resulting in a single string.

Answer 1

You want this:

object:addShape(unpack(values))

See also: http://www.lua.org/pil/5.1.html

Here's a complete example:

shape = {
  addShape = function(self, a, b, c)
    print(a)
    print(b)
    print(c)
  end
}

values = {1, 2, 3}
shape:addShape(unpack(values))

Answer 2

Whoever comes here and has Lua version > 5.1 unpack is moved into the table library so you can use: table.unpack

For more info: https://www.lua.org/manual/5.2/manual.html

Answer 3

This is not an answer about unpack, but a suggestion to use a different technique. Instead, do

function object:addShape(values)
    for i,v in ipairs(values) do 
        x,y = v.x, v.y
        ...
    end
end

function getPairs(values)
    xyPairs = {}
    for i=1,#values,2 do 
        v = {x=values[i], y=values[i+i] }
        table.insert(xyPair, v)
    end
    return xyPairs
end

values = {1, 1, 2, 2, 3, 3}
object:addShape(getPairs(values))

The amount of work to be done should be similar as unpacking and the additional processing you will have to do in addShape() to support variable number of named arguments.