Controlled Grammatic Ambiguity

Abstract

A new approach to ambiguity of context-free grammars is presented, and within this approach the LL and LR techniques are generalized to solve the following problems for large classes of ambiguous grammars: —Construction of a parser that accepts all sentences generated by the grammar, and which always terminates in linear time. —Identification of the structural ambiguity: a finite set of pairs of partial parse trees is constructed; if for each pair the two partial parse trees are semantically equivalent, the ambiguity of the grammar is semantically irrelevant. The user may control the parser generation so as to get a parser which finds some specific parse trees for the sentences. The generalized LL and LR techniques will still guarantee that the resulting parser accepts all sentences and terminates in linear time on all input. © 1994, ACM. All rights reserved.