local class = {}
 
function class.new(x, y, z)
    local mt = {__index = class,__add=class.add,__sub=class.sub,__mul=class.multiply,__div=class.divide}
  return setmetatable({["x"] = (x or 0), ["y"] = (y or 0), ["z"] = (z or 0)}, mt)
end
 
function class.add(self, other)
  assert(type(self) == "table", "Use : for operation")
  assert(type(other) == "table", "Unable to add "..type(other).." to vector")
  self.x = self.x + other.x
  self.y = self.y + other.y
  self.z = self.z + other.z
  return self
end
 
function class.sub(self, other)
  assert(type(self) == "table", "Use : for operation")
  assert(type(other) == "table", "Unable to sub "..type(other).." from vector")
  self.x = self.x - other.x
  self.y = self.y - other.y
  self.z = self.z - other.z
  return self
end
 
function class.multiply(self, scale)
  assert(type(self) == "table", "Use : for operation")
  assert(type(scale) == "number", "Unable to multiply "..type(scale).." with vector")
  self.x = self.x * scale
  self.y = self.y * scale
  self.z = self.z * scale
  return self
end
 
function class.divide(self, scale)
  assert(type(self) == "table", "Use : for operation")
  assert(type(scale) == "number", "Unable to divide "..type(scale).." with vector")
  self.x = self.x / scale
  self.y = self.y / scale
  self.z = self.z / scale
  return self
end
 
function class.dot(self, other)
  assert(type(self) == "table", "Use : for operation")
  assert(type(other) == "table", "Unable to dot "..type(other).." to vector")
  return (self.x * other.x + self.y * other.y + self.z * other.z)
end
 
function class.cross(self, other)
  assert(type(self) == "table", "Use : for operation")
  assert(type(other) == "table", "Unable to cross "..type(other).." to vector")
  return class.new(self.y * other.z - self.z * other.y,
                   self.z * other.x - self.x * other.z,
                   self.x * other.y - self.y * other.x)
end
 
function class.round(self)
  assert(type(self) == "table", "Use : for operation")
  self.x = math.floor(self.x + 0.5)
  self.y = math.floor(self.y + 0.5)
  self.z = math.floor(self.z + 0.5)
  return self  
end
 
function class.length(self)
  assert(type(self) == "table", "Use : for operation")
  return math.sqrt(self.x * self.x + self.y * self.y + self.z * self.z)
end
 
function class.normalize(self)
  assert(type(self) == "table", "Use : for operation")
  return class.divide(self, class.length(self))
end
 
function class.copy(self)
  assert(type(self) == "table", "Use : for operation")
  return class.new(self.x, self.y, self.z)
end
 
function class.toString(self)
  assert(type(self) == "table", "Use : for operation")
  return string.format("[%.3f, %.3f, %.3f]", self.x, self.y, self.z)
end
 
return class