14 research outputs found
The Sketch of a Polymorphic Symphony
In previous work, we have introduced functional strategies, that is,
first-class generic functions that can traverse into terms of any type while
mixing uniform and type-specific behaviour. In the present paper, we give a
detailed description of one particular Haskell-based model of functional
strategies. This model is characterised as follows. Firstly, we employ
first-class polymorphism as a form of second-order polymorphism as for the mere
types of functional strategies. Secondly, we use an encoding scheme of run-time
type case for mixing uniform and type-specific behaviour. Thirdly, we base all
traversal on a fundamental combinator for folding over constructor
applications.
Using this model, we capture common strategic traversal schemes in a highly
parameterised style. We study two original forms of parameterisation. Firstly,
we design parameters for the specific control-flow, data-flow and traversal
characteristics of more concrete traversal schemes. Secondly, we use
overloading to postpone commitment to a specific type scheme of traversal. The
resulting portfolio of traversal schemes can be regarded as a challenging
benchmark for setups for typed generic programming.
The way we develop the model and the suite of traversal schemes, it becomes
clear that parameterised + typed strategic programming is best viewed as a
potent combination of certain bits of parametric, intensional, polytypic, and
ad-hoc polymorphism
A Framework for Datatype Transformation
We study one dimension in program evolution, namely the evolution of the
datatype declarations in a program. To this end, a suite of basic
transformation operators is designed. We cover structure-preserving
refactorings, but also structure-extending and -reducing adaptations. Both the
object programs that are subject to datatype transformations, and the meta
programs that encode datatype transformations are functional programs.Comment: Minor revision; now accepted at LDTA 200
Strategic polymorphism requires just two combinators!
In previous work, we introduced the notion of functional strategies:
first-class generic functions that can traverse terms of any type while mixing
uniform and type-specific behaviour. Functional strategies transpose the notion
of term rewriting strategies (with coverage of traversal) to the functional
programming paradigm. Meanwhile, a number of Haskell-based models and
combinator suites were proposed to support generic programming with functional
strategies.
In the present paper, we provide a compact and matured reconstruction of
functional strategies. We capture strategic polymorphism by just two primitive
combinators. This is done without commitment to a specific functional language.
We analyse the design space for implementational models of functional
strategies. For completeness, we also provide an operational reference model
for implementing functional strategies (in Haskell). We demonstrate the
generality of our approach by reconstructing representative fragments of the
Strafunski library for functional strategies.Comment: A preliminary version of this paper was presented at IFL 2002, and
included in the informal preproceedings of the worksho
Typed Generic Traversal With Term Rewriting Strategies
A typed model of strategic term rewriting is developed. The key innovation is
that generic traversal is covered. To this end, we define a typed rewriting
calculus S'_{gamma}. The calculus employs a many-sorted type system extended by
designated generic strategy types gamma. We consider two generic strategy
types, namely the types of type-preserving and type-unifying strategies.
S'_{gamma} offers traversal combinators to construct traversals or schemes
thereof from many-sorted and generic strategies. The traversal combinators
model different forms of one-step traversal, that is, they process the
immediate subterms of a given term without anticipating any scheme of recursion
into terms. To inhabit generic types, we need to add a fundamental combinator
to lift a many-sorted strategy to a generic type gamma. This step is called
strategy extension. The semantics of the corresponding combinator states that s
is only applied if the type of the term at hand fits, otherwise the extended
strategy fails. This approach dictates that the semantics of strategy
application must be type-dependent to a certain extent. Typed strategic term
rewriting with coverage of generic term traversal is a simple but expressive
model of generic programming. It has applications in program transformation and
program analysis.Comment: 85 pages, submitted for publication to the Journal of Logic and
Algebraic Programmin
FOAL 2004 Proceedings: Foundations of Aspect-Oriented Languages Workshop at AOSD 2004
Aspect-oriented programming is a paradigm in software engineering and FOAL logos courtesy of Luca Cardelli programming languages that promises better support for separation of concerns. The third Foundations of Aspect-Oriented Languages (FOAL) workshop was held at the Third International Conference on Aspect-Oriented Software Development in Lancaster, UK, on March 23, 2004. This workshop was designed to be a forum for research in formal foundations of aspect-oriented programming languages. The call for papers announced the areas of interest for FOAL as including, but not limited to: semantics of aspect-oriented languages, specification and verification for such languages, type systems, static analysis, theory of testing, theory of aspect composition, and theory of aspect translation (compilation) and rewriting. The call for papers welcomed all theoretical and foundational studies of foundations of aspect-oriented languages. The goals of this FOAL workshop were to: � Make progress on the foundations of aspect-oriented programming languages. � Exchange ideas about semantics and formal methods for aspect-oriented programming languages. � Foster interest within the programming language theory and types communities in aspect-oriented programming languages. � Foster interest within the formal methods community in aspect-oriented programming and the problems of reasoning about aspect-oriented programs. The papers at the workshop, which are included in the proceedings, were selected frompapers submitted by researchers worldwide. Due to time limitations at the workshop, not all of the submitted papers were selected for presentation. FOAL also welcomed an invited talk by James Riely (DePaul University), the abstract of which is included below. The workshop was organized by Gary T. Leavens (Iowa State University), Ralf L?ammel (CWI and Vrije Universiteit, Amsterdam), and Curtis Clifton (Iowa State University). The program committee was chaired by L?ammel and included L?ammel, Leavens, Clifton, Lodewijk Bergmans (University of Twente), John Tang Boyland (University of Wisconsin, Milwaukee), William R. Cook (University of Texas at Austin), Tzilla Elrad (Illinois Institute of Technology), Kathleen Fisher (AT&T Labs�Research), Radha Jagadeesan (DePaul University), Shmuel Katz (Technion�Israel Institute of Technology), Shriram Krishnamurthi (Brown University), Mira Mezini (Darmstadt University of Technology), Todd Millstein (University of California, Los Angeles), Benjamin C. Pierce (University of Pennsylvania), Henny Sipma (Stanford University), Mario S?udholt ( ?Ecole des Mines de Nantes), and David Walker (Princeton University). We thank the organizers of AOSD 2004 for hosting the workshop