The Essence of Nested Composition
Calculi with disjoint intersection types support an introduction form for intersections called the merge operator, while retaining a coherent semantics. Disjoint intersections types have great potential to serve as a foundation for powerful, flexible and yet type-safe and easy to reason OO languages. This paper shows how to significantly increase the expressive power of disjoint intersection types by adding support for nested subtyping and composition, which enables simple forms of family polymorphism to be expressed in the calculus. The extension with nested sub- typing and composition is challenging, for two different reasons. Firstly, the subtyping relation that supports these features is non-trivial, especially when it comes to obtaining an algorithmic version. Secondly, the syntactic method used to prove coherence for previous calculi with disjoint intersection types is too inflexible, making it hard to extend those calculi with new features (such as nested subtyping). We show how to address the first problem by adapting and extending the Barendregt, Coppo and Dezani (BCD) subtyping rules for intersections with records and coercions. A sound and complete algorithmic system is obtained by using an approach inspired by Pierce’s work. To address the second problem we replace the syntactic method to prove coherence, by a semantic proof method based on logical relations. Our work has been fully formalized in Coq, and we have an implementation of our calculus.
Fri 20 JulDisplayed time zone: Amsterdam, Berlin, Bern, Rome, Stockholm, Vienna change
16:00 - 17:15 | |||
16:00 25mResearch paper | FHJ: A Formal Model for Hierarchical Dispatching and Overriding ECOOP Research Papers Yanlin Wang University of Hong Kong, Haoyuan Zhang , Bruno C. d. S. Oliveira University of Hong Kong, China, Marco Servetto Victoria University of Wellington DOI | ||
16:25 25mResearch paper | Modeling infinite behaviour by corules ECOOP Research Papers Davide Ancona University of Genova, Francesco Dagnino DIBRIS, University of Genova, Italy, Elena Zucca University of Genova DOI | ||
16:50 25mResearch paper | The Essence of Nested Composition ECOOP Research Papers Xuan Bi The University of Hong Kong, Bruno C. d. S. Oliveira University of Hong Kong, China, Tom Schrijvers KU Leuven DOI |