Polymorphic subtyping in O'Haskell

Polymorphi Subtyping in O'Haskell

Consistent Subtyping for All

Consistent subtyping is employed in some gradual type systems to validate type conversions. The original definition by Siek and Taha serves as a guideline for designing gradual type systems with subtyping. Polymorphic types à la System F also induce a subtyping relation that relates polymorphic types to their instantiations. However Siek and Taha’s definition is not adequate for polymorphic sub...

Rationale for O'Haskell

The construction of robust distributed and interactive software is still a challenging task, despite the recent popularity-increase for languages that take advanced programming concepts into the mainstream. Several problematic areas can be identified: most languages require the reactivity of a system to be manually upheld by careful avoidance of blocking operations; mathematical values often ne...

Subtyping First-Class Polymorphic Components

We present a statically typed, class-based object oriented language where classes are first class polymorphic values. A main contribution of this work is the design of a type system that combines first class polymorphic values with structural equirecursive types and admits a subtyping algorithm which is arguably much simpler than existing alternatives. Our development is modular and can be easi...

Polymorphic Subtyping Without Distributivity

The subtyping relation in the polymorphic second-order-calculus was introduced by John C. Mitchell in 1988. It is known that this relation is undecidable, but all known proofs of this fact strongly depend on the distributivity axiom. Nevertheless it has been conjectured that this axiom does not innuence the undecidability. The present paper shows undecidability of subtyping when we remove distr...