Parametric Compositional Data Types

Patrick Bahr
(Department of Computer Science, University of Copenhagen)
Tom Hvitved
(Department of Computer Science, University of Copenhagen)

In previous work we have illustrated the benefits that compositional data types (CDTs) offer for implementing languages and in general for dealing with abstract syntax trees (ASTs). Based on Swierstra's data types à la carte, CDTs are implemented as a Haskell library that enables the definition of recursive data types and functions on them in a modular and extendable fashion. Although CDTs provide a powerful tool for analysing and manipulating ASTs, they lack a convenient representation of variable binders. In this paper we remedy this deficiency by combining the framework of CDTs with Chlipala's parametric higher-order abstract syntax (PHOAS). We show how a generalisation from functors to difunctors enables us to capture PHOAS while still maintaining the features of the original implementation of CDTs, in particular its modularity. Unlike previous approaches, we avoid so-called exotic terms without resorting to abstract types: this is crucial when we want to perform transformations on CDTs that inspect the recursively computed CDTs, e.g. constant folding.

In James Chapman and Paul Blain Levy: Proceedings Fourth Workshop on Mathematically Structured Functional Programming (MSFP 2012), Tallinn, Estonia, 25 March 2012, Electronic Proceedings in Theoretical Computer Science 76, pp. 3–24.
Published: 11th February 2012.

ArXived at: bibtex PDF
References in reconstructed bibtex, XML and HTML format (approximated).
Comments and questions to:
For website issues: