Memoizing a monadic mixin DSL

Modular extensibility is a highly desirable property of a domain-specific language (DSL): the ability to add new features without affecting the implementation of existing features. Functional mixins (also known as open recursion) are very suitable for this purpose. We study the use of mixins in Haskell for a modular DSL for search heuristics used in systematic solvers for combinatorial problems, that generate optimized C++ code from a high-level specification. We show how to apply memoization techniques to tackle performance issues and code explosion due to the high recursion inherent to the semantics of combinatorial search. As such heuristics are conventionally implemented as highly entangled imperative algorithms, our Haskell mixins are monadic. Memoization of monadic components causes further complications for us to deal with

From types to type requirements: Genericity for model-driven engineering

The final publication is available at Springer via http://dx.doi.org/10.1007/s10270-011-0221-0Model-driven engineering (MDE) is a software engineering paradigm that proposes an active use of models during the development process. This paradigm is inherently type-centric, in the sense that models and their manipulation are defined over the types of specific meta-models. This fact hinders the reuse of existing MDE artefacts with other meta-models in new contexts, even if all these meta-models share common characteristics. To increase the reuse opportunities of MDE artefacts, we propose a paradigm shift from type-centric to requirement-centric specifications by bringing genericity into models, meta-models and model management operations. For this purpose, we introduce so-called concepts gathering structural and behavioural requirements for models and meta-models. In this way, model management operations are defined over concepts, enabling the application of the operations to any meta-model satisfying the requirements imposed by the concept. Model templates rely on concepts to define suitable interfaces, hence enabling the definition of reusable model components. Finally, similar to mixin layers, templates can be defined at the meta-model level as well, to define languages in a modular way, as well as layers of functionality to be plugged-in into other meta-models. These ideas have been implemented in MetaDepth, a multi-level meta-modelling tool that integrates action languages from the Epsilon family for model management and code generation.This work has been sponsored by the Spanish Ministry of Science and Innovation with projects METEORIC (TIN2008-02081) and Go Lite (TIN2011-24139), and by the R&D program of the Community of Madrid with project “e-Madrid” (S2009/TIC-1650)

What Does Aspect-Oriented Programming Mean for Functional Programmers?

Aspect-Oriented Programming (AOP) aims at modularising crosscutting concerns that show up in software. The success of AOP has been almost viral and nearly all areas in Software Engineering and Programming Languages have become "infected" by the AOP bug in one way or another. Interestingly the functional programming community (and, in particular, the pure functional programming community) seems to be resistant to the pandemic. The goal of this paper is to debate the possible causes of the functional programming community's resistance and to raise awareness and interest by showcasing the benefits that could be gained from having a functional AOP language. At the same time, we identify the main challenges and explore the possible design-space

The programming language jigsaw: mixins, modularity and multiple in heritance

technical reportThis dissertation provides a framework for modularity in programming languages. In this framework known as Jigsaw, inheritance is understood to be an essential linguistic mechanism for module manipulation. In Jigsaw, the roles of classes in existing languages are "unbundled," by providing a suite of operators independently controlling such effects as combination, modification encapsulation name resolution and sharing all on the single notion of module. All module operators are forms of inheritance Thus, inheritance is not in conflict with modularity in this system but is indeed its foundation This allows a previously unobtainable spectrum of features to be combined in a cohesive manner including multiple inheritance mixins, encapsulation and strong typing. Jigsaw has a rigorous semantics based upon a denotational model of inheritance Jigsaw provides a notion of modularity independent of a particular computational paradigm Jigsaw can therefore be applied to a wide variety of languages especially special purpose languages where the effort of designing specific mechanisms for modularity is difficult to justify but which could still benefit from such mechanisms. The framework is used to derive an extension of Modula-3 that supports the new operations An efficient implementation strategy is developed for this extension The performance of this scheme is on a par with the methods employed by the highest performance object oriented language processors currently available

Architectural Refactoring for Fast and Modular Bioinformatics Sequence Search

Bioinformaticists use the Basic Local Alignment Search Tool (BLAST) to characterize an unknown sequence by comparing it against a database of known sequences, thus detecting evolutionary relationships and biological properties. mpiBLAST is a widely-used, high-performance, open-source parallelization of BLAST that runs on a computer cluster delivering super-linear speedups. However, the Achilles heel of mpiBLAST is its lack of modularity, adversely affecting maintainability and extensibility; an effective architectural refactoring will benefit both users and developers. This paper describes our experiences in the architectural refactoring of mpiBLAST into a modular, high-performance software package. Our evaluation of five component-oriented designs culminated in a design that enables modularity while retaining high-performance. Furthermore, we achieved this refactoring effectively and efficiently using eXtreme Programming techniques. These experiences will be of value to software engineers faced with the challenge of creating maintainable and extensible, high-performance, bioinformatics software

super-Charging Object-Oriented Programming Through Precise Typing of Open Recursion

We present a new variation of object-oriented programming built around three simple and orthogonal constructs: classes for storing object state, interfaces for expressing object types, and mixins for reusing and overriding implementations. We show that the latter can be made uniquely expressive by leveraging a novel feature that we call precisely-typed open recursion. This features uses "this" and "super" annotations to express the requirements of any given partial method implementation on the types of respectively the current object and the inherited definitions. Crucially, the fact that mixins do not introduce types nor subtyping relationships means they can be composed even when the overriding and overridden methods have incomparable types. Together with advanced type inference and structural typing support provided by the MLscript programming language, we show that this enables an elegant and powerful solution to the Expression Problem