Featherweight Java

Abstract

Several recent studies have introduced lightweight versions of Java: reduced languages in which complex features like threads and reflection are dropped to enable rigorous arguments about key properties such as type safety. We carry this process a step further, omitting almost all features of the full language (including interfaces and even assignment) to obtain a small calculus, Featherweight Java, for which rigorous proofs are not only possible but easy. Featherweight Java bears a similar relation to Java as the lambda-calculus does to languages such as ML and Haskell. It offers a similar computational "feel," providing classes, methods, fields, inheritance, and dynamic typecasts with a semantics closely following Java's. A proof of type safety for Featherweight Java thus illustrates many of the interesting features of a safety proof for the full language, while remaining pleasingly compact. The minimal syntax, typing rules, and operational semantics of Featherweight Java make it a handy tool for studying the consequences of extensions and variations. As an illustration of its utility in this regard, we extend Featherweight Java with generic classes in the style of GJ (Bracha, Odersky, Stoutamire, and Wadler) and give a detailed proof of type safety. The extended system formalizes for the first time some of the key features of GJ.

A Provably Correct Compilation of Functional Languages into Scripting Languages

“….]" delimit an optional part of the syntax, we use x , y, z for variable names, 22 P. Giannini, A. Shaqiri e :: = x | n | tr | fls | F | e+e | if e then e else e | e e | e, e | let [mutable] x :T =e in e | let rec w :T =F in e | x <-e | raise e | try e with x -> e expression F :: = fun x :T ->e function T :: = int | bool | T → T type Figure 1: Syntax of core F# and the overbar sequence notation is used according to [15]. For instance: " x :T =F " stands for " x 1 :T 1 =F 1 · · · x n :T n =F n ".…”

Type qualifier inference for java

“…We present three type systems: Core JQual, which is a fieldbased, context-insensitive inference system, FS JQual, a field-sensitive extension, and CS/FS JQual, which further adds context-sensitivity. We describe both systems for the source language in Figure 3, which is a variation of Featherweight Java [22] that has been extended with qualifiers. Programs P consists of a sequence of class definitions L. Each class extends exactly one other class, and there is a built-in base class Object.…”

“…We formalize type qualifier inference as a system called Core JQual, which operates on a variant of Featherweight Java [22] with optional type qualifier annotations.…”

A Distributed Object-Oriented Language with Session Types

“…for π-calculus-based formalisms [4,5,13,15,17,25], for CORBA [26], for a λ-calculus with side-effects [14], for a multi-threaded functional language [27], and recently, for a W3C standard description language for web services called Choreography Description Language (CDL) [29]. To our knowledge, the integration of session types into an object-oriented language (even a small, core calculus, as in [3,10,18]) has not been attempted so far.…”

“…To focus on the introduction of session types, L doos does not include language features such as exceptions [2], synchronisation, serialisation [1], class (down)loading [1,11], code or agent mobility [1,7,28], polymorphism [6,18,27], recursive types [26] or correspondence assertions [4,5]. We believe that the inclusion of such features into L doos is possible, albeit not necessarily trivial.…”