High Quality Content by WIKIPEDIA articles! In computer science, a canonical LR parser or LR(1) parser is an LR(k) parser for k=1, i.e. with a single lookahead terminal. The special attribute of this parser is that all LR(k) parsers with k>1 can be transformed into a LR(1) parser. It can handle all deterministic context-free languages but is mostly avoided because of its high memory requirements in favor of less powerful but more efficient alternatives such as the LALR and the LL(1) parser.