CFLtype

CFLtype is a term encountered in some texts to denote a classification scheme for context-free languages (CFLs) according to the grammar or automaton that generates or recognizes them. The phrase is not a single standardized notion across all literature, but is used to discuss variants within the Chomsky Type-2 languages. In this sense, CFLtypes encompass subcategories such as deterministic context-free languages (DCFLs), which admit recognition by a deterministic pushdown automaton; and various parsing-restricted CFLs such as LL(k) or LR(k) grammars that permit efficient bottom-up or top-down parsing. The class of linear context-free languages (LCFLs), where productions have at most one nonterminal on the right-hand side, is another example sometimes discussed under CFLtype.

CFLtype emphasizes the relationship between the formal grammar form and the computational model, alongside practical parsing considerations. For instance, DCFLs are strictly more constrained than general CFLs and allow deterministic parsing algorithms, which is relevant for compiler construction. Context-free languages in general are closed under union, concatenation, and Kleene star but not under intersection or complementation, a facet often cited when characterizing CFLtype distinctions.

The term often appears in theoretical discussions about the limits of context-free formalisms, such as the boundaries between CFLs and more powerful language classes, or in surveys comparing parsing strategies for programming languages. See also Chomsky hierarchy, context-free language, deterministic context-free language, pushdown automaton, LL(k), LR(k).