Some classifications of context-free languages
نویسندگان
چکیده
منابع مشابه
Nonterminal Complexity of Some Operations on Context-Free Languages
We investigate context-free languages with respect to the measure Var of descriptional complexity, which gives the minimal number of nonterminals which is necessary to generate the language. Especially, we consider the behaviour of this measure with respect to operations. For given numbers c1, c2, . . . , cn and an nary operation τ on languages we discuss the range of Var(τ(L1, L2, . . . , Ln))...
متن کاملThe Inclusion Problem for Some Subclasses of Context-Free Languages
− By a reduction to Post’s Correspondence Problem we provide a direct proof of the known fact that the inclusion problem for unambiguous context-free grammars is undecidable. The argument or some straightforward modification also applies to some other subclasses of context-free languages such as linear languages, sequential languages, and DSClanguages (i.e., languages generated by context-free ...
متن کاملThe Inclusion Problem of Context-Free Languages: Some Tractable Cases
We study the problem of testing whether a context-free language is included in a fixed set L0, where L0 is the language of words reducing to the empty word in the monoid defined by a complete string rewrite system. We prove that, if the monoid is cancellative, then our inclusion problem is polynomially reducible to the problem of testing equivalence of straight-line programs in the same monoid....
متن کاملTape Bounds for Some Subclasses of Deterministic Context-Free Languages
There are several interesting observations to be made concerning the tape complexity of context-free languages. An early result given by Lewis et al. (1965) is that every context-free language can be recognized by an off-line deterministic Turing machine of O((log n) 2) tape complexity. This is still the best result known. Sudborough (1975) shows that if all linear context-free languages can be...
متن کاملSome Results on Top-Context-Free Tree Languages
Top context free tree languages called cor gulier by Arnold and Dauchet constitute a natural subclass of context free tree languages In this paper we give further evidence for the importance of this class by exhibiting certain closure properties We systematically treat closure under the operations replacement and substitution as well as under the corresponding iteration operations Several other...
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ژورنال
عنوان ژورنال: Information and Control
سال: 1969
ISSN: 0019-9958
DOI: 10.1016/s0019-9958(69)90055-2