Summary: Higher-Order Subtyping for Dependent Types
Department of Computer Science
Institute of Cybernetics, Tallinn, Estonia
24 November 2011
Andreas Abel (LMU) Subtyping Dependent IOC 2011 1 / 32
A is a subtype of B, written A B, if a value of type A can be supplied
wherever a value of type B is demanded.
Pos Nat. A function that can handle natural numbers n Nat,
meaning n 0, is not embarrased by a positive number n Pos,
meaning n > 0.
List Pos List Nat. If I can process a list of natural numbers, I can
process a list of positive numbers.
Nat Pos Pos Nat. I want a function that turns positive