Mixin Composition Synthesis based on Intersection Types

We present a method for synthesizing compositions of mixins using type inhabitation in intersection types. First, recursively defined classes and mixins, which are functions over classes, are expressed as terms in a lambda calculus with records. Intersection types with records and record-merge are used to assign meaningful types to these terms without resorting to recursive types. Second, typed terms are translated to a repository of typed combinators. We show a relation between record types with record-merge and intersection types with constructors. This relation is used to prove soundness and partial completeness of the translation with respect to mixin composition synthesis. Furthermore, we demonstrate how a translated repository and goal type can be used as input to an existing framework for composition synthesis in bounded combinatory logic via type inhabitation. The computed result is a class typed by the goal type and generated by a mixin composition applied to an existing class

MIXIN COMPOSITION SYNTHESIS BASED ON INTERSECTION TYPES

We present a method for synthesizing compositions of mixins using type inhabitation in intersection types. First, recursively defined classes and mixins, which are functions over classes, are expressed as terms in a lambda calculus with records. Intersection types with records and record-merge are used to assign meaningful types to these terms without resorting to recursive types. Second, typed terms are translated to a repository of typed combinators. We show a relation between record types with record-merge and intersection types with constructors. This relation is used to prove soundness and partial completeness of the translation with respect to mixin composition synthesis. Furthermore, we demonstrate how a translated repository and goal type can be used as input to an existing framework for composition synthesis in bounded combinatory logic via type inhabitation. The computed result is a class typed by the goal type and generated by a mixin composition applied to an existing class

Featherweight Jigsaw - Replacing inheritance by composition in Java-like languages

none3We present FJig, a simple calculus where basic building blocks are classes in the style of Featherweight Java, declaring fields, methods and one constructor. However, inheritance has been generalized to the much more flexible notion originally proposed in Bracha's Jigsaw framework. That is, classes play also the role of modules, that can be composed by a rich set of operators, all of which can be expressed by a minimal core. Fields and methods can be declared of four different kinds (abstract, virtual, frozen, local) determining how they are affected by the operators. We keep the nominal approach of Java-like languages, that is, types are class names. However, a class is not necessarily a structural subtype of any class used in its defining expression. While this allows a more flexible reuse, it may prevent the (generalized) inheritance relation to be a subtyping relation. So, the required subtyping relations among classes are declared by the programmer and checked by the type system. The calculus allows the encoding of a large variety of different mechanisms for software composition in class-based languages, including standard inheritance, mixin classes, traits and hiding. Hence, FJig can be used as a unifying framework for analyzing existing mechanisms and proposing new extensions. We provide two different semantics of an FJig program: flattening and direct semantics. The difference is analogous to that between two intuitive models to understand inheritance: the former where inherited methods are copied into heir classes, and the latter where member lookup is performed by ascending the inheritance chain. Here we address equivalence of these two views for a more sophisticated composition mechanism.mixedG. Lagorio; M. Servetto; E. ZuccaLagorio, Giovanni; M., Servetto; Zucca, Elen

Non-reformist reform for Haskell Modularity

In this thesis, I present Backpack, a new language for building separately-typecheckable packages on top of a weak module system like Haskell’s. The design of Backpack is the first to bring the rich world of type systems to the practical world of packages via mixin modules. It’s inspired by the MixML module calculus of Rossberg and Dreyer but by choosing practicality over expressivity Backpack both simplifies that semantics and supports a flexible notion of applicative instantiation. Moreover, this design is motivated less by foundational concerns and more by the practical concern of integration into Haskell. The result is a new approach to writing modular software at the scale of packages.Modulsysteme wie die in Haskell erlauben nur eine weiche Art der Modularität, in dem Modulimplementierungen direkt von anderen Implementierungen abhängen und in dieser Abhängigkeitsreihenfolge verarbeitet werden müssen. Modulsysteme wie die in ML andererseits erlauben eine kräftige Art der Modularität, in dem explizite Schnittstellen Vermutungen über Abhängigkeiten ausdrücken und jeder Modultyp überprüft und unabhängig ergründet werden kann. In dieser Dissertation präsentiere ich Backpack, eine neue Sprache zur Entwicklung separattypenüberprüfbarer Pakete über einem weichen Modulsystem wie Haskells. Das Design von Backpack überführt erstmalig die reichhaltige Welt der Typsysteme in die praktische Welt der Pakete durch Mixin-Module. Es wird von der MixML-Kalkulation von Rossberg und Dreyer angeregt. Backpack vereinfacht allerdings diese Semantik durch die Auswahl von Anwendbarkeit statt Expressivität und fördert eine flexible Art von geeigneter Applicative- Instantiierung. Zudem wird dieses Design weniger von grundlegenden Anliegen als von dem praktischen Anliegen der Eingliederung in Haskell begründet. Die Semantik von Backpack wird durch die Ausarbeitung in Mengen von Haskell-Modulen und „binary interface files“ definiert, und zeigt so, wie Backpack Interoperabilität mit Haskell erhält, während Backpack es mit Schnittstellen nachrüstet. In meiner Formalisierung Backpacks präsentiere ich ein neuartiges Typsystem für Haskellmodule und überprüfe einen entscheidenen Korrektheitssatz, um die Semantik von Backpack zu validieren.Max Planck Institute for Software Systems (MPI-SWS