This paper addresses the longstanding problem of the recognition limitations of classical LALR(1) parser generators by proposing the usage of noncanonical parsers. To this end, we present a definition of noncanonical LALR(1) parsers, NLALR(1). The class of grammars accepted by NLALR(1) parsers is a proper superclass of the NSLR(1) and LALR(1) grammar classes. Among the recognized languages are some nondeterministic languages. The proposed parsers retain many of the qualities of canonical LALR(1) parsers: they are deterministic, easy to construct, and run in linear time. We argue that they could provide the basis for a range of powerful noncanonical parsers.
Key words: deterministic parsing, noncanonical parsing, LALR(1), valid covers, two-stack pushdown automata.
