A powerful LL(k) covering transformation

Abstract

k-transformable grammars have been conjectured to be the uppermost class of LL(k) covering transformable grammars. PLR(k) grammars have been known as a well characterized subclass of k-transformable grammars. Being contrary to those claims, this paper shows that some PLR( k) grammars are not k-transformable, and so k-transformable grammars are not the true uppermost. A powerful LL( k) covering transformation is suggested in this paper. It is a generalization of the transformations of k-transformable grammars and PLR( k) grammars. A remarkable aspect of the new transforming process is the deterministic property, where "deterministic" means that the transformation is obtained in a single process without requiring any heuristic, unlike k-transformable grammars' transformation for which a heuristic is required. The transformable grammar class is shown to be larger than k-transformable grammars and PLR( k) grammars.