Translating Python to Haskell, keeping core concepts

1_class.py

# A simple class in Python
class car():
  # The __init__ method
  def __init__(self, color):
    self.color = color
 
  # The color method
  def color(self):
    return self.color
 
  # The mpg method
  def mpg(self):
    return 45
 
# Construct a car object then call the mpg method.
if __name__ == '__main__':
  c = car('red')
  # Note that car.mpg(c) is the same as c.mpg()
  print car.mpg(c)

2_class.hs

-- A simple class in Haskell
data Car = Car String
 
-- Function for constructing a new car
-- This takes the place of the __init__ method
car color = Car color
 
-- The color function
color (Car color) = color
 
-- The mpg function
mpg (Car _) = 45
 
-- Construct a car object then call the mpg method.
main =
  let c = car "red"
  in print (mpg c)

3_inheritance.py

# A simple class in Python
class car():
  # The __init__ method
  def __init__(self, color):
    self.color = color
 
  # The color method
  def color(self):
    return self.color
 
  # The mpg method
  def mpg(self):
    return 45
 
# Basic inheritance
class truck(car):
  # The overridden mpg method
  def mpg(self):
    return 14
 
# Construct a truck object then call the mpg method.
if __name__ == '__main__':
  t = truck('red')
  print truck.mpg(t)

4_inheritance.hs

-- A simple class in Haskell
data Car = Car String
         | Truck String -- Basic inheritance
 
-- Function for constructing a new car
-- This takes the place of the __init__ method
car color = Car color
 
-- The color function
color (Car color) = color
 
-- The mpg function
-- Both the truck and car variants are handled here
mpg c = case c of
          (Car _) -> 45
          (Truck _) -> 14
 
-- Function for constructing a new truck
-- This takes the place of the __init__ method
truck color = Truck color
 
-- Construct a car object then call the mpg method.
main =
  let t = truck "red"
  in print (mpg t)