From Attribute Grammars to Constraint Handling Rules

Abstract

Attribute grammars provide a framework to de ne compu- tations over trees, by decorating those trees with attributes. Attribute grammars have been successfully applied in many areas, including compiler construction and natural language processing. In this paper we present a translation of attribute grammars to Constraint Handling Rules, a formalism based on constraint rewriting. Our translation is able to express in a simple way several extensions to attribute grammars. Higher-order attributes are attributes whose value is again a tree, for which attributes can be computed recursively. Look- ahead enables attribute de nitions to depend not only on the current node, but also on the shape of its subtrees. Specialization provides a way to override the default computation of an attribute when some conditions are met; a natural way to de ne exceptions to the default tree processing.