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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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For the grammar given, provide 3 valid example strings

today I got a homework on my 'Programming Languages' class and I'm having trouble. Here is the full question; For the grammars given below, draw transition diagram and transition table. Provide 3 valid example strings. And this is the one I'm…
cbt
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Kleene Closure for infinite subset

Let L = {an | n >= 0}, where and for all n >= 1. Thus L consists of sequences of a of all lengths, including a sequence of length 0. Let L2 be any infinite subset of L. I need to show there always exists a DFA to recognize (L2)*. If L2 is a…
Aditya Nambiar
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Left Linear Grammar: How to construct?

I need help constructing a Left Linear grammar for the language L = { a^n b^m c^p | n>=2, m>=3, p>=4 } Here is what I have so far, I know : N = {S} T = { a, b, c } P = { S -> Pcccc P -> Pc P -> M M -> Mbbb M ->Mb M -> N N ->Naa N->a } I need…
Mike
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How to handle floating point numbers in shunting-yard algorithm

I am coding an engineering calculator in C and in in-fix to post-fix conversion which I coded an state-machine for it, I am using shunting-yard algorithm. In order to handle floating point numbers, I decided to use a stack with double blocks for the…
Melika Barzegaran
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Is the following language regular? context free?

Given the following language: L = { bi | i > 0 } U {aibi | i > 0 } Is this language context free? regular? I tried thinking about it, but no results so far..
Rouki
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Prove that a language is regular

Given the regular languages L1 and L2, prove that the following language is also regular: I know that U,*,. between 2 regular languages provides a regular language. But, the following regular language is infinite so I don't really have an idea how…
Rouki
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Navigating a Turing Machine

Say I'm in state q5 with the following input: 000[q5]100 I'm about to read in a 1 and my instructions are 1->x,L while moving to q6 Would the tape then look like this? 00[q6]0x00? I'm not sure what to do when reading something from the right but…
user2853262
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Deterministic finite automata - state diagram

If I have to draw a deterministic finite automata using a state diagram so that accepts a language, for example {λ ε {a,b}*: the word λ contains an even number of a and an odd number of b}, how do I know how many states I have?
Mary Star
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How to construct the DFA for the regular expression of a real number?

I'm trying to construct the Definite Finite Automata of a real number, that is defined as a string leading with an optional '+' or '-', followed by a single zero or non-empty sequence of digits that doesn't start with a zero. This is followed by a…
user1893199
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Writing GNF grammar for a CFL

Hello I would like to ask you this question. I was supposed to compute (manually) a grammar in Greibach Normal Form, that generates the language L = {ai bj ck | i + j = 2k and k >= 1} I really have no idea. Can someone please help me? Thanks in…
user2799534
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Do epsilon transitions in an nfa accept any input?

If i have this transition in my nfa epsilon ( q1 ) ----------------> ( q2 ) for the alphabet {a,b} does that mean that there is a transtion from q1 to q2 when either b or a is read as input when the nfa is in state q1? Or are there no…
kjh
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(Homework) Converting an NFA to a DFA with an epsilon transition, but no transition for some a in the alphabet

If my alphabet is {a,b} and my nfa has the following transitions: State | a b epsilon -------------------------------------------- q0 q1 null q1 q1 q2 q1 none q2 …
kjh
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Can a deterministic finite acceptor begin at the end of string and move toward the start?

If so, how is this drawn as a graph? what would you label your start state? and would you draw the graph as moving from right to left as well?
kjh
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how to design full text search algorithm where keyword quantity is huge (like Google Alerts)?

I am building something very similar to Google Alerts. If you don't know what it is, consider the following scenario, Thousands of new textual articles, blog posts influx everyday Each user has a list of favorite "keywords" that he'd like to…
est
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Deterministic Finite Automata of a simple arithmetic string

Would this DFA solve the problem to create a DFA that accepts simple arithmetic string. e.g. 7 -> accepted 4+1 -> accepted 5-7 -> accepted 8*3 -> accepted 2/1 -> accepted * -> not accepted /3 -> not…
Joey Hipolito
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