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Abstract

The objective of the Cristal group is to study type systems for programming and to develop statically-typed programming languages and tools for typed programming.

Our main current topics are: design and development of the Caml programming language, the study of the usage of statically-typed programming languages for developing Web-related tools, and true theoretical study of types : objects, subtyping and polymorphism.

The Caml programming language is a statically-typed functional programming language with a non-obtrusive type system (types are inferred by the compiler), polymorphism, imperative features and a powerful exception mechanism. Caml-Light is a portable lightweight implementation, well suited for teaching and is widely used in undergraduate and graduate curricula. Caml-Light is available under Unix, MacOS and Microsoft Windows. During 1996, we started distributing Objective Caml, which features an expressive module system, an extremely efficient native code compiler, and a class-based object layer, compatible with type inference.

We have developed and distributed a Web browser called MMM and a personal Web proxy called V6, demonstrating that efficient, large-scale applications can be programmed in Caml. The originality of MMM is that it accepts Caml programs as applets, where static typechecking and cryptographic tools are used to ensure that applets are harmless.

We study type systems for objects and subtyping, and use research results for improving the Objective Caml object system. Polymorphism is one of our other interests, particularly extensional polymorphism and intersection type systems, and their relationship with lambda-calculus and beta-reduction. We are also working on mechanical proofs of type inference algorithms.

All our developments, as well as a description of our activities, are available on our Web server : http://pauillac.inria.fr/cristal.