منابع مشابه
Pushdown 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 ...
متن کاملEfficient Universal Pushdown Cellular Automata and Their Application to Complexity
In order to obtain universal classical cellular automata an in nite space is required. Therefore, the number of required processors depends on the length of input data and, additionally, may increase during the computation. On the other hand, Turing machines are universal devices which have one processor only and additionally an in nite storage tape. Here an in some sense intermediate model is ...
متن کاملReducing Deep Pushdown Automata
This contribution presents reducing variant of the deep pushdown automata. Deep pushdown automata is a new generalization of the classical pushdown automata. Basic idea of the modification consists of allowing these automata to access more deeper parts of pushdown and reducing strings to non-input symbols in the pushdown. It works similarly to bottom-up analysis simulation of context-free gramm...
متن کاملTrimming Visibly Pushdown Automata
We study the problem of trimming visibly pushdown automata (VPA). We first describe a polynomial time procedure which, given a visibly pushdown automaton that accepts only well-nested words, returns an equivalent visibly pushdown automaton that is trimmed. We then show how this procedure can be lifted to the setting of arbitrary VPA. Furthermore, we present a way of building, given a VPA, an eq...
متن کامل2-Visibly Pushdown Automata
Visibly Pushdown Automata (VPA) are a special case of pushdown machines where the stack operations are driven by the input. In this paper, we consider VPA with two stacks, namely 2-VPA. These automata introduce a useful model to effectively describe concurrent pushdown systems using a simple communication mechanism between stacks. We show that 2-VPA are strictly more expressive than VPA. Indeed...
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ژورنال
عنوان ژورنال: Theoretical Computer Science
سال: 1999
ISSN: 0304-3975
DOI: 10.1016/s0304-3975(97)00187-4