Haskell-Syntax für Komponenten-Namen

• bisher: positionelle Notation der Konstruktor-Argumente

  data Tree a = Leaf | Branch (Tree a) a (Tree a)
  t = Branch Leaf "bar" Leaf
  case t of Branch l k r -> k
  

• alternativ: Notation mit Komponentennamen:

  data Tree a = Leaf 
    | Branch {left::Tree a, key::a, right::Tree a }
  t = Branch {left=Leaf,key="bar",right=Leaf}
  case t of Branch {} -> key t
  

• kann auch gemischt verwendet werden:

  Branch {left=Leaf,key="bar"
         ,right=Branch Leaf "foo" Leaf}