Animal = {
  name = "Animalia"
}

function Animal:eat()
  print ("(Animal) " .. self.name .. " is eating")
end

function Animal:new(o)
  o = o or {}
  setmetatable(o, self)
  self.__index = self
  return o
end

Mammal = Animal:new {
  name = "Mammalia"
}

function Mammal:eat()
  print ("(Mammal) " .. self.name .. " is eating")
end

function Mammal:suck()
  print ("(Mammal) " .. self.name .. " is sucking milk")
end

Dog = Mammal:new {
  name = "Canis lupus familiaris"
}

function Dog:eat()
  print ("(Dog) " .. self.name .. " is eating")
end

function Dog:bark()
  print ("(Dog) " .. self.name .. " is barking")
end

-- Working with the original object prototypes:
print("Working with the original object prototypes");
Animal:eat();
Mammal:eat();
Dog:eat();
Mammal:suck();
Dog:suck();
Dog:bark();

-- Working with object instances:
print("Working with object instances");
a = Animal:new {}
m = Mammal:new {}
d0 = Dog:new {}
d1 = Dog:new {name = "Tigrinho"}
a:eat();
m:eat();
d0:eat();
d1:eat();
m:suck();
d0:suck();
d0:bark();
d1:suck();
d1:bark();