Towards safe and flexible object adaptation

In this paper, a programming language NextEJ is proposed. NextEJ is based on Epsilon model, which realizes object adaptation to contexts. The novelty of Epsilon model is its ability to make objects be able to freely enter or leave contexts dynamically and belong to multiple contexts at a time. However, such kind of flexibility also easily brings type-unsafety. NextEJ tackles this problem by introduc-ing a new feature called context activation scope. Inside a context activation scope, it is assured that an object is al-ways bound with the role activated so that no method-not-understood errors occur at run-time. Furthermore, context activation scope can be nested so that multiple contexts can be activated at a time. A role instance has a pre-defined field thisContext which refers to its enclosing context instance. In the case of multiple context activations, the reference of thisContext is interpreted as a composite context whose behavior is determined by the order of activations

Towards Practical Gradual Typing

Over the past 20 years, programmers have embraced dynamically-typed programming languages. By now, they have also come to realize that programs in these languages lack reliable type information for software engineering purposes. Gradual typing addresses this problem; it empowers programmers to annotate an existing system with sound type information on a piecemeal basis. This paper presents an implementation of a gradual type system for a full-featured class-based language as well as a novel performance evaluation framework for gradual typing

A Type System for First-Class Layers with Inheritance, Subtyping, and Swapping

Context-Oriented Programming (COP) is a programming paradigm to encourage modularization of context-dependent software. Key features of COP are layers---modules to describe context-dependent behavioral variations of a software system---and their dynamic activation, which can modify the behavior of multiple objects that have already been instantiated. Typechecking programs written in a COP language is difficult because the activation of a layer can even change objects' interfaces. Inoue et al. have informally discussed how to make JCop, an extension of Java for COP by Appeltauer et al., type-safe. In this article, we formalize a small COP language called ContextFJ$_{<:}$ with its operational semantics and type system and show its type soundness. The language models main features of the type-safe version of JCop, including dynamically activated first-class layers, inheritance of layer definitions, layer subtyping, and layer swapping