Lua Academy · Lesson

Varargs and the ... Operator

Handle variable-length argument lists using ... and select().

Variable Arguments

A Lua function can accept a variable number of arguments using ... (three dots) in the parameter list. Inside the function, ... represents the extra arguments. You can use it in expressions, pass it to other functions, or convert it to a table.

local function sum(...)
  local total = 0
  for _, v in ipairs({...}) do
    total = total + v
  end
  return total
end

print(sum(1, 2, 3))        -- 6
print(sum(10, 20, 30, 40)) -- 100

select() for Varargs

select(n, ...) returns arguments from position n onward. select("#", ...) returns the total count of arguments including nil values. This is safer than #{...} which stops at the first nil hole.

local function inspect(...)
  local n = select("#", ...)
  print("count:", n)
  for i = 1, n do
    print(i, select(i, ...))
  end
end

inspect("a", "b", nil, "d")
-- count: 4
-- 1  a
-- 2  b
-- 3  nil
-- 4  d

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