Higher-order subtyping with intersection types

Contains fulltext : mmubn000001_194713903.pdf (publisher's version ) (Open Access)Promotores : M. Dezani-Ciancaglini en H. BarendregtX, 160 p

A Typeful Approach to Object-Oriented Programming with Multiple Inheritance

The wide practice of objected oriented programming (OOP) in current software practice is evident. Despite extensive studies on typing programming objects, it is still undeniably a challenging research task to design a type system that can satisfactorily account for a variety of features (e.g., binary methods and multiple inheritance) in OOP. In this paper, we present a typeful approach to implementing objects that makes use of a recently introduced notion of guarded datatypes. In particular, we demonstrate how the feature of multiple inheritance can be supported with this approach, presenting a simple and general account for multiple inheritance in a typeful manner

Complexity of kernel Fun subtype checking

System kernel Fun is an abstract version of the system Fun defined by Cardelli's and Wegner's seminal paper [CW85], and is strictly related to system F≤. Extensions of these two systems are currently the basis of most proposals for strong type systems for object-oriented languages. We study here the problem of subtype checking for system kernel Fun, presenting the following results. We show that the standard kernel Fun subtype checking algorithm has an exponential complexity, and generates an exponential number of different subproblems. We then present a new subtype checking algorithm which has a polynomial complexity. In the process we study how variable names can be managed by a kernel Fun subtype checker which is not based on the De Bruijn encoding, and we show how to perform kernel Fun subtype checking with a `constraint generating' technique. The algorithm we give is described by a set of type rules, which we prove to be equivalent to the standard one. This new presentation of kernel Fun type system is characterized by a `multiplicative' behaviour, and it may open the way to new presentations for system F≤ as well

Feature-Oriented Programming with Object Algebras

Object algebras are a new programming technique that enables a simple solution to basic extensibility and modularity issues in programming languages. While object algebras excel at defining modular features, the composition mechanisms for object algebras (and features) are still cumbersome and limited in expressiveness. In this paper we leverage two well-studied type system features, intersection types and type-constructor polymorphism, to provide object algebras with expressive and practical composition mechanisms. Intersection types are used for defining expressive run-time composition operators (combinators) that produce objects with multiple (feature) interfaces. Type-constructor polymorphism enables generic interfaces for the various object algebra combinators. Such generic interfaces can be used as a type-safe front end for a generic implementation of the combinators based on reflection. Additionally, we also provide a modular mechanism to allow different forms of self-references in the presence of delegation-based combinators. The result is an expressive, type-safe, dynamic, delegation-based composition technique for object algebras, implemented in Scala, which effectively enables a form of Feature-Oriented Programming using object algebras