GLR Parser

A GLR parser (GLR standing for "generalized left-to-right") is an extension of an LR parser algorithm to handle nondeterministic and ambiguous grammars. First described in a 1984 paper by Masaru Tomita, it has also been referred to as a "parallel parser". Tomita presented five stages in his original work, though in practice it is the second stage that is recognized as the GLR parser.

Though the algorithm has evolved since its original form, the principles have remained intact: Tomita's goal was to parse natural language text thoroughly and efficiently. Standard LR parsers cannot accommodate the nondeterministic and ambiguous nature of natural language, and the GLR algorithm can.