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Questions tagged [decidable]

Decidable languages are languages such that the problem of whether a given word belongs to it or not is decidable. A decision problem, i.e., a question with a yes/no answer, is called decidable if there exists an algorithm (a Turing machine) that can and will return a Boolean true or false value (instead of looping indefinitely).

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Is a given TM having finite states is decidable or not?

first of all is above question is correct? i think decidability is property of particular problem like 1. whether given string belong to particular language 2. whether TM will reach particular state on given input and not of TM(or any other machine…
Viraat Saxsena
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How to define a subformula of an inductively defined type in Agda?

I'm trying to define a simple predicate to determine if a formula is a subformula of a given formal over a simple inductively defined syntax. I'm running into a few, presumably simple, problems. (i) I'd rather use a parameterized module with a…
user5775230
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What is the prefix of L={⟨M⟩ | M is TM that accepts every palindrome over its alphabet }?

I am trying to find the prefix of L={⟨M⟩ | M is TM that accepts every palindrome over its alphabet }, but I am not sure how to do it since it involves a Turing Machine in it. Does anyone have any ideas? Thank you!
Michael
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Is OWL2 + SWRL math built ins decidable?

I know that reasoning doesn't work in general when combining SWRL and OWL2 because the combination is not decidable. However, it is decidable when only certain things/rules are used. So assuming I only want to use the SWRL math built-ins, is…
quarky
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Proving A Language Is Undecidable Using Turing Reductions

I need to prove that the language L(EVEN) = { M : |L(M)| is even } is undecidable. In other words, the language L(EVEN) is the set of all Turing Machines which accept some language of even cardinality. Here, M is the encoding of some Turing…
kmoney22z
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Show that the language is undecidable

Consider the language Consider the language Aabb = {< M > | M is a TM, and M accepts abb} a) What is the computational problem that is represented by Aabb? b) Show that Aabb is undecidable. I tried proving it but didn't know what to do.
Youssef Karam
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Whether a context free language is deterministic context free language

Let L(G) be the language generated by a context free grammar G. Is the following decision problem decidable ?Whether L(G) is deterministic context free language ? I understood why the above problem is undecidable from this link, but I had a…
mahesh Rao
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How to demonstrate a set is decidible, semi-decidible or not semi-decidible?

I have been asked to prove if the following set is decidible, semi-decidible or not semi-decidible: In other words, it is the set of inputs such that exists a Turing Machine encoded with the natural y with input p that returns its input. Consider…
Mick
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Is a primarily prime TM decidable?

A language L over alphabet Σ is primarily prime if and only if for every length l, the majority of strings of length l do belong to L if l is a prime number, but do not belong to L if l is a composite number. Let PriPriTM = {〈M〉 : L(M) is primarily…
turingnoob
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Finite State Machine procedure

I need to Design an efficient decision procedure to determine if the language accepted by a non-deterministic Finite state machine is empty. I know machine doesn't accepting string if there is no path from initial state to final state. But I'm…
user10543640
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Is there a non-RE language that is composed of only 1 element?

I read in a book (Hromkovic, Communication Complexity and Parallel Computating) that there is an infinite number of non recursively - enumerable (non-RE) languages that are composed of only 1 element? But is that possible? I though that for a…
Link L
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Is a CFG using a nil language decidable?

If I have a Context-Free Grammar G such that the language of G is nil, is G decidable? I know the answer is yes, but I am having trouble proving this. My first thought is to say there is only one state, q1, which is the start state and accept state…
Darkhydro
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Something is not computable, can it be co-recursively enumerable?

My understanding is since it is not computable, it may not halt when the answer is 'yes' or 'no'. That's why it cannot be co-recursively enumerable since it can't guarantee it always halts on 'no'.
sharprabbitz
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Decidability of "Is n divisible with 23?"

I have the following problem: Let n be a natural number, n > 10^100. Is n divisible with 23? Is this problem semi-decidable or decidable? It is possible to create an algorithm to find the answer such that it would always halt. I am pretty confused…
Toma Radu-Petrescu
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Implement enumerator using turing machine - redundant prints

In the following algorithm: we implement an enumerator using a turing machine and the enumerator is supposed to output the language accepted by the turing machine. The accepted words from Σ* are printed multiple times (each iteration previously…
caffein
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