An efficient class and object encoding

Abstract

An object encoding translates a language with object primitives to one without. Similarly, a class encoding translates classes into other primitives. Both are important theoretically for comparing the expressive power of languages and for transferring results from traditional languages to those with objects and classes. Both are also important foundations for the implementation of object-oriented languages as compilers typically include a phase that performs these translations. This paper describes a language with a primitive notion of classes and objects and presents an encoding of this language into one with records and functions. The encoding uses two techniques often used in compilers for single-inheritance class-based object-oriented languages: the self-application semantics and the method-table technique. To type the output of the encoding, the encoding uses a new formulation of self quantifiers that is more powerful than previous approaches.

Type-Safe Method Inlining

“…Transformations of programs in these languages must produce programs in these languages themselves, and in particular produce programs that still type check-a property called typability preservation. In a similar sense, a number of recent compilers use typed intermediate languages (e.g., [5][6][7][8]) to obtain debugging and optimisation benefits [5,9]. Such compilers also require transformations that are typability preserving when translating from one typed representation to another.…”

Subtyping for F-Bounded Quantifiers and Equirecursive Types

“…For example, it can require a type that has a method that returns an object of the type being bounded. This form of bound is useful for binary methods and in typing object encodings [Gle00]. Treating a type variable as being a subtype of its bound when that bound can refer to it is like treating a recursive type as being equal to its unrolling, and similar issues arise to formalising such type systems.…”