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Questions tagged [pushdown-automaton]

A pushdown automaton (PDA) is a finite-state automaton with added stack based memory. It is a mathematical description of an algorithm for parsing context-free languages.

PDAs extend finite automata via a stack-based memory, and transitions can push/pop symbols to/from the stack. Deterministic PDAs (ones for which there exists only one legal transition at any time) are strictly weaker than non-deterministic ones; such is not the case for finite automata (PDAs are more powerful) or Turing machines (PDAs are weaker).

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PDA and a regular expression

I have a PDA and some regular expression. Is there any algorithm I can use to make sure my PDA accepts strings that are subset of what could be produced by the regular expression ? Thanks! Gil
Tomer
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PDA for L = {a^nb^m : m ≥ n, m-n is even}

Design a PDA for the following language L = {a^nb^m : m ≥ n, m-n is even}.
Pramodya Mendis
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Gradually transitioning FSM

It is given that a particular object can have two states at any point in time and that the object transitions from one state to another gradually. I am modeling the state-graph to capture all the possible states the object can have and their…
Mahesh
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Applying PDA transitions over a list of input strings in haskell

I'm trying to implement a PDA in Haskell based on my lecturer's notes, she has described the general process to us and left the actual function implementation up to us. I feel like I have the majority of it working bar one little bug in the…
Jambo
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Describe a Pushdown Automata for this language

We define the language ABC inductively as: epsilon is in ABC. if x is in ABC then so are [x] and (x), if x and y are both in ABC then so is xy. Describe a PDA for this language which accepts by empty stack. Give all transitions.
lily once
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DFA to PDA conversion

I am looking for an algorithm to convert a Deterministic Finite Automata to Push Down Automata. Any help appreciated. Thanks!
iBiryukov
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Let Σ = { a; b} How can I define a PDA in JFLAP which recognizes the following?

L = {a^n b^k | 2n >= k} For example.: abb is element of L, aabbb is element of L, ε is element of L, but babbb is not element of L, abbb is not element of L
Viktor
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Prove that the language is context free

How can we design a PDA for the language L= {w | number of 010s in w is more than the number of 101s} to prove it is context free
Divya
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Can every DFA be simulated by a PDA?

Given a Deterministic Finite Automata (DFA) M_1, does there always exist a Pushdown Automata (PDA) M_2 that accepts the same language as M_1? I.e. can any DFA be simulated by a PDA? Intuitively, it makes sense to me that a PDA is more powerful…
Paradox
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Context Free Grammar to PDA

Can this grammar be converted to a PDA? `S-> aS | EPSILON ` I think no because I cannot define how much “a” to push-pop.
user9039337
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Create a pushdown automata for the following language

So I was doing practice problems in my book and I spotted this question. Construct an npda accepting the language L on sigma(a,b,c). L={w: number of a= number of b+1} so I am interpreting it as it accepts all strings that has one more a then the…
Derek Yee
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Program to convert context free language to push down automata?

I can't find any applet or program online to convert a context free language into a push down automata... any help would be greatly appreciated.
MadSeb
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What languages are accepted in the PDA

I'm struggling to understand the notation of push down automata's when pushing and popping items on and off of stacks. I understand that the stack must be empty for the string to be accepted. Here is my PDA: If I create a transition diagram for…
snuffles101
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Creating a syntax tree with pushdown automation?

If I were to create a pushdown automation that accepts a state(name) and those states accept transitions(input, pop, push, nextState). How does all this help me construct a parse tree? I mean a pushdown automata is great for checking if something is…
Asperger
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Nondeterministic Pushdown Automata different diagrams

In introduction to the theory of computation book, for the language a state diagram is given as : I know there could be alternative diagrams but I doubt the solution I found might be wrong which is slightly different than the original one: I…
Nili Miliy
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