Haskell record syntax and type classes

Question

Suppose that I have two data types Foo and Bar. Foo has fields x and y. Bar has fields x and z. I want to be able to write a function that takes either a Foo or a Bar as

Answer 1

You could use code such as

data Foo = Foo { fooX :: Int, fooY :: Int } deriving (Show)
data Bar = Bar { barX :: Int, barZ :: Int } deriving (Show)

instance HasX Foo where
  getX = fooX
  setX r x' = r { fooX = x' }

instance HasX Bar where
  getX = barX
  setX r x' = r { barX = x' }

What are you modeling in your code? If we knew more about the problem, we could suggest something less awkward than this object-oriented design shoehorned into a functional language.