Deterministic context-free grammar

In formal grammar theory, the deterministic context-free grammars (DCFGs) are a proper subset of the context-free grammars. They are the subset of context-free grammars that can be derived from deterministic pushdown automata, and they generate the deterministic context-free languages. DCFGs are always unambiguous, and are an important subclass of unambiguous CFGs; there are non-deterministic unambiguous CFGs, however.

DCFGs are of great practical interest, as they can be parsed in linear time and in fact a parser can be automatically generated from the grammar by a parser generator. They are thus widely used throughout computer science. Various restricted forms of DCFGs can be parsed by simpler, less resource-intensive parsers, and thus are often used. These grammar classes are referred to by the type of parser that parses them, and important examples are LALR, SLR, and LL.