-- Inheritance: shape prototype:
shape_proto= {family="shape"}
function shape_proto:get_species() return self.species end
function shape_proto:get_family() return self.family end

setmetatable(rectangle_proto, {__index=shape_proto})
setmetatable(circle_proto, {__index=shape_proto})

print(circle:get_family().."/"..circle:get_species()) --> shape/circle
print(rectangle:get_family().."/"..rectangle:get_species()) --> shape/rectangle