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{Bots|deny=AWB}}<!--REASON: incorrectly identifies the first "{" in "{[[empty string{{!}}ε]]}" as an unbalanced bracket & removes it--> thumb|right|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 st... Tags: Mobile edit Mobile web edit |
→Properties: clarified the Gilman-Shapiro result & connected it to the Muller-Schupp theorem |
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{{Bots|deny=AWB}}<!--REASON: incorrectly identifies the first "{" in "{[[empty string{{!}}ε]]}" as an unbalanced bracket & removes it-->
[[File:Pushdown-overview.svg|thumb|right|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 [[
Like a [[stack automaton]], a nested stack automaton may step up or down in the stack, and read the current symbol; in addition, it may at any place create a new stack, operate on that one, eventually destroy it, and continue operating on the old stack. This way, stacks can be nested recursively to an arbitrary depth; however, the automaton always operates on the innermost stack only.
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An example run (input string not shown):
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When automata are allowed to re-read their input ("[[Two-way automaton|two-way automata]]"), nested stacks do not result in additional language recognition capabilities, compared to plain stacks.<ref>{{cite journal |last1=Beeri |first1=C. |title=Two-way nested stack automata are equivalent to two-way stack automata |journal=Journal of Computer and System Sciences |date=June 1975 |volume=10 |issue=3 |pages=317–339 |doi=10.1016/s0022-0000(75)80004-3 |doi-access=free }}</ref>
Gilman and Shapiro used nested stack automata to solve the [[Word problem for groups|word problem]] in
==Notes==
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