LALR parsers handle more grammars than SLR parsers. These languages assist with generating lexical analyzers and parsers for context-free grammars. This table compares parser generators with parsing expression grammars, deterministic boolean grammars. Non-deterministic pushdown automata are another formalism equivalent to context-free grammars. Cognitive grammar is unorthodox with respect to generative grammars and American structuralism. Many wrote grammars and compiled dictionaries. Not all descriptive grammars recognize tritransitive verbs. Bernese German grammars and dictionaries also exist. For learning of more general grammars, see Grammar induction. An LR(1) parser can handle many but not all common grammars. The operators are used in rewrite rules for generative grammars. Surviving dictionaries are a century earlier than their grammars. This produces the formalism of context-sensitive grammars. This is essential for ambiguous grammars such as used for human languages. The following are some decidable problems about context-free grammars.