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Code code:"if (foo != bar)"
Sections title:apples
body:"apples oranges"
URL url:"*.example.com"
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Questions about problems which cannot be solved by any Turing machine.

1 vote
1 answer
542 views

How to prove the language of all Turing Machines that accept an undecidable language is unde...

I want to prove that $L=\{\langle M \rangle |L(M)\text{ is undecidable}\}$ is undecidable I am not sure about this. This is my try : Suppose L is decidable. Let $E$ be the decider from $L$. Let $A$ be …
Frank's user avatar
  • 147
0 votes
1 answer
149 views

Is the languague L={<M>, M accepts a finite amount of words} decdidable?

Is $L=\{<M> | L(M) \ is \ finite\} $ decidable ? M is a TM. I think its relative simple to proof with the theorem of rice. But I am interested in a solution which does not use the Rice theorem. This m …
Frank's user avatar
  • 147
0 votes

Is every subset of a decidable set, also decidable?

Its not true. Proof : Let $A=\Sigma^*$,we know that $A$ is decidable. Now lets take a look at $$ \Sigma^*\cap A_{TM}=A_{TM}$$ Since $\Sigma^*$ is the Set which contains all languagues it also contain …
Frank's user avatar
  • 147
-1 votes
1 answer
18 views

Is the Languague which contains all TMs which write the blank symbol at firs by the given in...

Consider the problem of determining whether a Turing machine M on an input w writes the blank symbol at first. Is this decidable ?
Frank's user avatar
  • 147