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Questions tagged [automata]

In theoretical computer science, automata theory is the study of abstract 'mathematical' machines or systems and the computational problems that can be solved using these machines. These abstract machines are called automata. ("Automata", Wikipedia)

From Wikipedia,

Automata, or automata theory, is the study of mathematical objects called abstract machines or automata and the computational problems that can be solved using them. Automata comes from the Greek word αὐτόματα meaning "self-acting".

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Kripke structure

What is a (pseudocode) algorithm for checking invariant over Kripke structures, such that in case the invariant is violated, the counterexample returned by the algorithm is of minimal length?
Rinad Rama
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Making an index for a search by PHP

How can you search only unique words with PHP such that I can learn the basics in making the search? I have had a few problems in making a multidimensional array for questions. My first unsuccessful attempt is the following. #1 $result =…
Léo Léopold Hertz 준영
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Show bit strings with count(1s) = count(0s) isn't regular

Let L be the language consisting of strings over alphabet {0,1} that contain an equal number of 1s and 0s. For example: 000111 10010011 10 1010101010 How can you show that L isn't a regular language?
Andrew Tomazos
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Pumping lemma in PDA and CFL

I have an pumping lemma question I totally stuck on... L = {w ∈ {a, b, c}∗ : na (w) < nb (w) < nc (w)} is it CFL or not? I quest it is not CFL because it is not enough to have one stack to remember al those conditions. You can remember that na (w)…
erogol
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Is the following union of CFL and non-CFL CFL itself?

I'm a TA, and was asked the following by a student. Embarrassingly, I couldn't come up with an answer, so I turn to you guys. We know that L_1 = {a^n b^n c^n} is non-CFL. We also know that L_2 = {a^i b^k c^j : i != k } is context free. What about…
Shir
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Shortest distance in the log semiring for a weighted automaton

I thought I'd figured this out... but I still cannot wrap my head around it. I'm playing with OpenFst and trying to figure out how 'shortestdistance' is calculated in the 'log' semiring. For the following little…
user1179499
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Application of Brzozowski Algebraic Method on this FA

Earlier, I asked a question on here asking for help with the conversion of a transition-graph of a finite automaton into a regular expression: Understanding (and forming) the regular expression of this finite automaton Thanks to the user Patrick87,…
finitenessofinfinity
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Understanding (and forming) the regular expression of this finite automaton

For the above automaton, the regular expression that has been given in my textbook is the following : a*(a*ba*ba*ba*)*(a+a*ba*ba*ba*) I am having trouble deriving this...the following is my attempt at it : aa* + aa*(ba*ba*ba*)* + ba*ba*ba* +…
finitenessofinfinity
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How to convert NFA/DFA to java?

I have a scenario where I have designed the NFA and using JFLAP I have converted it to DFA. I need to know, how to code it in Java? Basically how to implement those state transitions in Java. I have seen some examples which do this using switch and…
Inco Mob
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Finding regular expressions for languages otherwise described

Letting {a b} be the alphabet set, write a regular expression for: 1) The language of all those words in which the number of a's and the number of b's are both odd; 2) The language of all those words whose length is odd and which contain the…
Mi7
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Regular expression for odd length of a's and odd length of b's

I am stuck in this question and took me 1 hour but still failed to solve it. The language can contain any combination of "a" and "b" but both a's and b's length must be odd (individual length not combined length of string) I tried to identify…
Alpha Gaming
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Turing machine to solve a^(0+1+2+3+....+n)

Can anyone give me some insight how that Turing machine can be implemented? L = Xa^n n >= 0 and n = 0 + 1 + 2 + 3 +....+ M accepted examples: Xa ->(0+1) Xaaa -> (0+1+2) Xaaaaaa (0+1+2+3) etc. I couldn't find any source on the…
Ugur Kellecioglu
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How to apply Kleene star on automata?

I know how to apply Kleene star on language but I'm not sure how would I apply it to DFA or NFA. I'm pretty sure it would need to be epsilon NFA with initial state that is final and final states might need epsilon transition to that initial…
qu4lizz
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Reachability analysis of a vertex in a graph, using Cellular Automata

Testing reachability of a node in a graph (directed), can be done using cellualr Automata? Actually what's in mind, is to implement an algorithm that checks reachability of a nod from a specified vertex, using CA. Is it even possible? Is CA capable…
Faria
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Need help to solve the function haskell regex manipulation function

The definition firsts :: RE sym -> [sym] firsts = undefined The RE data data RE sym -- sym is type of alphabet symbols = RSym sym -- match single symbol | REps -- match empty string | RZero -- match nothing | RStar (RE sym) --…
newlight
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