Two double-exponential gaps for automata with a limited pushdown
نویسندگان
چکیده
منابع مشابه
Input-Driven Double-Head Pushdown Automata
We introduce and study input-driven deterministic and nondeterministic double-head pushdown automata. A double-head pushdown automaton is a slight generalization of an ordinary pushdown automaton working with two input heads that move in opposite directions on the common input tape. In every step one head is moved and the automaton decides on acceptance if the heads meet. Demanding the automato...
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Recently, an infinite hierarchy of languages accepted by stateless deterministic pushdown automata has been established based on the number of pushdown symbols. However, the witness language for the nth level of the hierarchy is over an input alphabet with 2(n−1) elements. In this paper, we improve this result by showing that a binary alphabet is sufficient to establish this hierarchy. As a con...
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The linear-time simulation of 2-way deterministic pushdown automata (2DPDA) by the Cook and Jones constructions is revisited. Following the semantics-based approach by Jones, an interpreter is given which, when extended with random-access memory, performs a linear-time simulation of 2DPDA. The recursive interpreter works without the dump list of the original constructions, which makes Cook’s in...
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In the two-sided pushdown automata discussed in this paper, their two-sided pushdowns are introduced over free groups rather than free monoids. It is demonstrated that these automata with pushdowns introduced in this way characterize the family of recursively enumerable languages.
متن کاملPushdown Automata
Families of Languages AFL thm if F is closed under substitution with λ-free regular sets, morphism, union with regular sets [easy for cfg] & intersection with regular sets, then F is closed under inverse morphism Figure 26: closure properties of CF II 12 intersection with regular languages a;A/α a a;A/α λ;A/α λ;A/α { } } { ⇒ ⇒ { anbn | n ≥ 1 }∗ ∩ { w ∈ {a, b}∗ |#ax even } r1 p1 q1 r0 p0 q0 r p ...
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ژورنال
عنوان ژورنال: Information and Computation
سال: 2017
ISSN: 0890-5401
DOI: 10.1016/j.ic.2016.06.005