Type classes (mix-ins)

• Type class = special kind of module

  • some functions are virtual
  • specify the type of those functions (for static typing)
    • 1 ensure a common behaviour
  • write other functions using those virtual functions
    • 1 inclusion polymorphism

• Example:

  • class Eq(a) where
  • == :: a,a -> bool
  • x!=y = ! (x==y)
  • (this type is parametric, more about it in next slide)

Notes: