Lua by Example: Variadic Functions

Variadic functions can be called with any number of trailing arguments. For example, print is a common variadic function.

Here’s a function that will take an arbitrary quantity of numbers as arguments.

 
local function sum(...)
    print("items: ", ...)
    total = 0
    for idx, num in ipairs({...}) do
        total = total + num
    end
    print("total: ",total)
end

Variadic functions can be called in the usual way with individual arguments.

 
sum(1, 2)
sum(1, 2, 3)

If you already have multiple args in a slice, apply them to a variadic function using table.unpack().

 
nums = {1, 2, 3, 4}
sum(table.unpack(nums))
 
$ lua variadic-functions.lua
items:     1    2
total:     3
items:     1    2    3
total:     6
items:     1    2    3    4
total:     10

Another key aspect of functions in Lua is their ability to form closures, which we’ll look at next.

Next example: Methods.

by Blake Bourque | source | license