Simple Error Recovery Scheme for Optimized LR-Parsers

Abstract

A new, simple and effective method for syntactic error recovery in optimized (reduced) LR-parsers is presented. This method, called the Simple Recovery and Correction scheme, is phrase oriented and performs local and some form of global contect correction. The error handling mechanism is driven by information obtainable from an LR-parser decision table. The formal basis for the method is the concept of synchronizing triple. A theoretical characterization of synchronizing triples is given and algorithms for direct extraction of recovery control information are presented. As a part of the SRC scheme a simplified method for the organization of LR-parser forward moves is introduced. In the last part of the paper the performance of the SRC scheme is illustrated in a specific case and implementation problems are discussed.