Coupling evaluators for attribute coupled grammars

Abstract

Some years ago, the notion of attribute coupled grammars was introduced by Ganzinger and Giegerich [4], together with descriptional composition. The latter works essentially at the specification level, i.e., it produces an attribute grammar which specifies the composition of two attribute coupled grammars. We introduce a new approach to this composition of attribute coupled grammars. This composition no longer works at the specification level but at the evaluator level. It produces a special kind of attribute evaluator. For this purpose we have introduced the notion of coupling evaluator. The main advantage of this new approach, compared with descriptional composition, is that it is possible to build separately the coupling evaluator of each attribute coupled grammar; in other words it allows real separate compilation of AG modules. Another important advantage is that we do not need to check the attribute grammar class in order to construct the final sequence of evaluators; thus, this construction produces a new sort of evaluator.