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If a DPDA for this language exists, and it sees a string 0 n, it must use its stack to memorize the length n, in order to be able to distinguish its possible continuations 0 n 11 0 n ∈ L p and 0 n 11 0 n+2 ∉ L p. Hence, after reading 0 n 11 0 n, comparing the post-"11" length to the pre-"11" length will make the stack empty again.
[b] For many non-regular PDAs, any equivalent DPDA would require an unbounded number of states. A finite automaton with access to two stacks is a more powerful device, equivalent in power to a Turing machine. [8] A linear bounded automaton is a device which is more powerful than a pushdown automaton but less so than a Turing machine. [c]
The notion of the DCFL is closely related to the deterministic pushdown automaton (DPDA). It is where the language power of pushdown automata is reduced to if we make them deterministic; the pushdown automata become unable to choose between different state-transition alternatives and as a consequence cannot recognize all context-free languages. [1]
Nondeterministic pushdown automaton (also abbreviated NDPDA), Topics referred to by the same term This disambiguation page lists articles associated with the title NPDA .
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A transition without consuming an input symbol is called an ε-transition and is represented in state diagrams by an arrow labeled "ε". ε-transitions provide a convenient way of modeling systems whose current states are not precisely known: i.e., if we are modeling a system and it is not clear whether the current state (after processing some ...
A nested stack automaton has the same devices as a pushdown automaton, but has less restrictions for using them.. In automata theory, a nested stack automaton is a finite automaton that can make use of a stack containing data which can be additional stacks. [1]
An epsilon transition (also epsilon move or lambda transition) allows an automaton to change its state spontaneously, i.e. without consuming an input symbol. It may appear in almost all kinds of nondeterministic automaton in formal language theory, in particular: