vector.lua

-- Vector

local _prototype = {x=0, y=0, z=0}

function _prototype:tostring()
  local pattern = "Vector: (x=%.2f, y=%.2f, z=%.2f)"
  return string.format(pattern, self.x, self.y, self.z)
end

function _prototype:equal(other)
  return (self.x == other.x and
    self.y == other.y and
    self.z == other.z)
end

function _prototype:add(other)
  return new(
    self.x + other.x,
    self.y + other.y,
    self.z + other.z)
end

function _prototype:sub(other)
  return new(
    self.x - other.x,
    self.y - other.y,
    self.z - other.z)
end

local _mt = {
  __index = _prototype,
  __tostring = _prototype.tostring,
  __eq = _prototype.equal,
  __add = _prototype.add,
  __sub = _prototype.sub
}

function new(x, y, z)
  local o = {x=x, y=y, z=z}
  setmetatable(o, _mt)
  return o
end