-- Chapter 27 example: Point class.

local Point = {}
Point.__index = Point

function Point.new(x, y)
    local self = setmetatable({}, Point)
    self.x = x
    self.y = y
    return self
end

function Point:distance(other)
    local dx = self.x - other.x
    local dy = self.y - other.y
    return math.sqrt(dx * dx + dy * dy)
end

local a = Point.new(0, 0)
local b = Point.new(3, 4)
print(a:distance(b))   -- 5.0

-- Try-this: add Point:move(dx, dy) and call it on `a`.