A unifying model for lookahead LR parsing

Abstract

A construction method is presented for lookahead LR passers that unifies many of the construction algorithms available in the literature. The model allows single, multiple, and arbitrary symbol lookahead, each only when required. Three user-supplied parameters are used by the construction method; specific settings of these parameters yield well-known grammar classes such as LALR(k), SLR(k), and several subsets of the LR-regular class, among others. Thus. rather than using several severely incompatible parser generators, or making unnatural changes to the grammar to accommodate the parsing techniques, one can manipulate these parameters to obtain a suitable parsing technique. The model captures the essence of the problem of computing lookahead for LR parsers, and provides a better understanding of the relationships among the corresponding classes of context-free grammars.<>