Aspect AG

Attribute Grammars (AGs), a general-purpose formalism for describing recursive computations over data types, avoid the trade-off which arises when building software incrementally: should it be easy to add new data types and data type alternatives or to add new operations on existing data types? However, AGs are usually implemented as a pre-processor, leaving e.g. type checking to later processing phases and making interactive development, proper error reporting and debugging difficult. Embedding AG into Haskell as a combinator library solves these problems. Previous attempts at embedding AGs as a domain-specific language were based on extensible records and thus exploiting Haskell’s type system to check the well-formedness of the AG, but fell short in compactness and the possibility to abstract over oft occurring AG patterns. Other attempts used a very generic mapping for which the AG well-formedness could not be statically checked. We present a typed embedding of AG in Haskell satisfying all these requirements. The key lies in using HList-like typed heterogeneous collections (extensible polymorphic records) and expressing AG well-formedness conditions as type-level predicates (i.e., typeclass constraints). By further type-level programming we can also express common programming patterns, corresponding to the typical use cases of monads such as Reader, Writer and State. The paper presents a realistic example of type-class-based type-level programming in Haskell.

Papers

Title : Attribute Grammars Fly First-Class: How to do aspect oriented programming in Haskell

Authors : Marcos Viera, S. Doaitse Swierstra, Wouter S. Swierstra

Full Text : pdf

Slides : pdf

BibTeX : bib

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Title : UUAG Meets AspectAG: How to make Attribute Grammars First-Class

Authors : Marcos Viera, S. Doaitse Swierstra, Arie Middelkoop

Full Text : pdf

Slides :

BibTeX :

Benchmarks : Benchmarks

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Title : Attribute Grammars Macros

Authors : Marcos Viera, S. Doaitse Swierstra

Full Text : pdf

Slides :

BibTeX :

Packages

AspectAG : AspectAG (includes examples)

Examples

Oberon-0 : tar.gz (from the LDTA 2011 tool challenge)