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Combining Universal and Existential Quantification

• Combination
  • Universal quantification: generic types.
  • Existential quantification: abstract data types.
  • Combination: parametric data abstractions.

nil: forall a. List[a]
cons: forall a. (a x List[a]) -> List[a]
hd: forall a. List[a] -> a
tl: forall a. List[a] -> List[a]
Null: forall a. List[a] -> Bool

array: forall a. Int -> Array[a]
index: forall a. (Array[a] x Int) -> a
update: forall a. (Array[a] x Int x a) -> Unit