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Decidability Problems for Grammars
Some Reduction Inferences
Example reductions
Recent questions tagged decidability
0
votes
1
answer
181
ox cs education
alternate definition of semi decidable Definition: an enumerator for a language L ⊂ Σ ∗ is a TM that writes on its output tape #x1#x2#x3# . . . and L = {x1, x2, x3, . . .}. pleasee elaborate this http://www.cs.ox.ac.uk/people/paul.goldberg/FCS/slides3.pdf
Gurdeep Saini
asked
in
Theory of Computation
Nov 14, 2018
by
Gurdeep Saini
284
views
theory-of-computation
decidability
1
vote
0
answers
182
Decidability
Na462
asked
in
Theory of Computation
Nov 14, 2018
by
Na462
1.6k
views
decidability
theory-of-computation
turing-machine
recursive-and-recursively-enumerable-languages
1
vote
1
answer
183
Decidability
Na462
asked
in
Theory of Computation
Nov 14, 2018
by
Na462
412
views
decidability
theory-of-computation
recursive-and-recursively-enumerable-languages
0
votes
1
answer
184
Decidability
How to distinguish between a problem which is (undecidable) and which is (undecidable but partially decidable); or rather for a given problem how to say in which category it falls?
Mizuki
asked
in
Theory of Computation
Nov 14, 2018
by
Mizuki
470
views
decidability
theory-of-computation
turing-machine
recursive-and-recursively-enumerable-languages
1
vote
2
answers
185
Decidability
Decidable or Undecidable? Given a Turing machine M, a string s and an integer k, M accepts s within k steps. Please elaborate.
Mizuki
asked
in
Theory of Computation
Nov 14, 2018
by
Mizuki
525
views
decidability
theory-of-computation
turing-machine
recursive-and-recursively-enumerable-languages
1
vote
3
answers
186
Decidability
Given two deterministic CFG G$_1$ and G$_2$, is L( G$_1$ ) = L( G$_2$ ) ?
Shamim Ahmed
asked
in
Theory of Computation
Nov 1, 2018
by
Shamim Ahmed
1.3k
views
decidability
theory-of-computation
context-free-language
0
votes
0
answers
187
Decidability
Given two deterministic CFG G$_1$ and G$_2$ , is L(G$_1$) ∩ L(G$_2$) = ∅ ?
Shamim Ahmed
asked
in
Theory of Computation
Nov 1, 2018
by
Shamim Ahmed
514
views
decidability
theory-of-computation
context-free-language
1
vote
1
answer
188
Reducibility Problem
Consider 2 problems X & Y. Now if X is reducible to Y.What does this mean.please explain with an example.
Lovejeet Singh
asked
in
Theory of Computation
Oct 30, 2018
by
Lovejeet Singh
504
views
reducibilty
decidability
theory-of-computation
0
votes
0
answers
189
Undecidability
L1:{<M> | there exist a Turing machine M' such that <M>$\neq$<M'> and L(M) = L(M')} How this problem becomes trivial? and if it non-trivial then please explain why is that so. According to my understanding, non-trivial ... is then is it okay to say M1=M2 because they are kind of same machine but other one is just with some non deterministic nature.
Swapnil Naik
asked
in
Theory of Computation
Oct 30, 2018
by
Swapnil Naik
548
views
theory-of-computation
rice-theorem
turing-machine
decidability
0
votes
0
answers
190
Decidability Doubt
A recursive language is empty or a recursive language contains all strings over sigma*. Why this problem is undecidable?
aditi19
asked
in
Theory of Computation
Oct 29, 2018
by
aditi19
254
views
decidability
theory-of-computation
turing-machine
recursive-and-recursively-enumerable-languages
0
votes
0
answers
191
turing machine decidability
Given a turing machine M ,state q, and string 'w' whether M ever moves its head to the left when started with input w is decidable or undecidable ? explain ?
Gurdeep Saini
asked
in
Theory of Computation
Oct 28, 2018
by
Gurdeep Saini
320
views
decidability
5
votes
1
answer
192
DECIDABILITY
L = {<M> | L(M) = {1}} L = {<M> | L(M) is {} } L = {<M> | L(M) has exactly 100 strings} which are REC R E BUT not REC , NOT EVEN RE
Smishra95
asked
in
Theory of Computation
Oct 16, 2018
by
Smishra95
621
views
decidability
recursive-and-recursively-enumerable-languages
theory-of-computation
3
votes
2
answers
193
Decidability
$L_1= \{\langle M\rangle \mid $ there exists $x \in \Sigma^*$ such that for every $y \in L(M), xy \notin L(M)\}.$ Is $L_1$ RE or not RE?
Somoshree Datta 5
asked
in
Theory of Computation
Oct 8, 2018
by
Somoshree Datta 5
2.2k
views
recursive-and-recursively-enumerable-languages
decidability
0
votes
1
answer
194
doubt
What is semi and Partially decidable...and how we know
bhavnakumrawat5
asked
in
Theory of Computation
Oct 1, 2018
by
bhavnakumrawat5
650
views
decidability
1
vote
1
answer
195
Decidability
Let A, B, C and D are problems. Consider the following polynomial reductions to known about the problem B. (i) AB (A is reducible to B) (ii) C D (iii) B D Find the correct statement from the following 1.. if A is decidable, B is decidable 2. if D is undecidable, B is undecidable 3. if C is decidable, B is decidable 4. if A is undecidable, B is undecidable
aditi19
asked
in
Theory of Computation
Sep 26, 2018
by
aditi19
836
views
decidability
0
votes
0
answers
196
undecidability
Writes Non Blank: Given a turing machine T, does it ever writes a non-blank symbol on its tape, when started with a blank tape. how the above problem is solvable? somewhere i got this explanation: Let the machine only writes blank symbol. Then ... is a non-trivial property of turing machine and every non trivial property of turing machine is undecidable, so this is also undecidable.
aambazinga
asked
in
Theory of Computation
Sep 21, 2018
by
aambazinga
454
views
theory-of-computation
decidability
rice-theorem
turing-machine
1
vote
1
answer
197
Decidability-12.9.5
Let $L_1$ be a regular language and G be a context-free grammar. Show that the problem "$L_1 \subseteq L(G)$" is undecidable.
Ayush Upadhyaya
asked
in
Theory of Computation
Sep 17, 2018
by
Ayush Upadhyaya
734
views
decidability
theory-of-computation
1
vote
2
answers
198
Decidability
Let M1 be a Turing machine and M2 be a finite automaton. Is the problem, whether M1 and M2 accept the same language decidable? An elaborative answer with proof is most welcome.
Ayush Upadhyaya
asked
in
Theory of Computation
Sep 17, 2018
by
Ayush Upadhyaya
529
views
decidability
theory-of-computation
0
votes
0
answers
199
TM that rejects input string x
$D = \left \{ <M> \mid \ M \text{ is a TM that rejects the input string } x \right \}$ What is complement of D and is it Decidable, Turing recognizable or not Turing recognizable?
Mk Utkarsh
asked
in
Theory of Computation
Sep 15, 2018
by
Mk Utkarsh
517
views
decidability
1
vote
1
answer
200
TM that accepts input string x
$D = \left \{ M \mid \ M \text{ is a TM that accepts the input string } x \right \}$ What is complement of D and is it Decidable, Turing recognizable or not Turing recognizable?
Mk Utkarsh
asked
in
Theory of Computation
Sep 15, 2018
by
Mk Utkarsh
1.5k
views
theory-of-computation
decidability
turing-machine
0
votes
0
answers
201
Decidable / Undecidable (Acceptance of CFL)
A Turing Machine accepts a language if its DCFL but rejects if it's a non deterministic CFL
Mk Utkarsh
asked
in
Theory of Computation
Sep 15, 2018
by
Mk Utkarsh
564
views
decidability
theory-of-computation
1
vote
1
answer
202
Decidable / Undecidable
Given a regular language, does the language contain any string at all. Given a regular language, does the language contain infinite number of strings. Given a recursive language, does the language contain infinite number of strings. Given a recursive language, does the language contain any string at all.
Mk Utkarsh
asked
in
Theory of Computation
Sep 15, 2018
by
Mk Utkarsh
448
views
decidability
theory-of-computation
3
votes
2
answers
203
Decidability (Acceptance problem)
Whether the given languages are recursive, recursively enumerable or non RE 1) $L = \left \{ <M> | <M> \ accepts \ all \ strings \ of \ length \ at \ most \ 5 \right \}$ 2) $L = \left \{ <M> | <M> \ accepts \ strings \ of \ length \ at \ most \ 5 \right \}$
Mk Utkarsh
asked
in
Theory of Computation
Sep 14, 2018
by
Mk Utkarsh
1.1k
views
theory-of-computation
decidability
turing-machine
0
votes
0
answers
204
Turing machine
Consider <M> be the encoding of a TM as a string over the alphabet {0,1}. Consider L = {<M> | M is a TM that halts on all the input and L(M) = L' for some Undecidable language L' } then L is ? A. Decidable and Recursive B. Decidable and Non recursive C. Undecidable and RE D. Undecidable and Non RE
Na462
asked
in
Theory of Computation
Sep 9, 2018
by
Na462
255
views
turing-machine
recursive-and-recursively-enumerable-languages
decidability
0
votes
0
answers
205
Relationship b/w closure and decidability?
Is there any relationship b/w closure and decidability? Thanks
surbhijain93
asked
in
Theory of Computation
Sep 9, 2018
by
surbhijain93
313
views
theory-of-computation
decidability
closure-property
0
votes
0
answers
206
self doubt
CAN SOMEONE EXPLAIN ME WITH AN EXAMPLE THAT WHY DCFL CLOSED UNDER COMPLEMENATION AND CFL NOT CLOSED UNDER COMPLEMENATION?
sushmita
asked
in
Theory of Computation
Sep 9, 2018
by
sushmita
183
views
theory-of-computation
closure-property
decidability
0
votes
0
answers
207
TOC- Undecidability
sidlewis
asked
in
Theory of Computation
Sep 8, 2018
by
sidlewis
424
views
theory-of-computation
decidability
rice-theorem
context-free-language
turing-machine
0
votes
0
answers
208
TOC Decidability
How can we say that any two disjoint co-turing recognisable languages are seperable by some Decidability language?
aambazinga
asked
in
Theory of Computation
Sep 8, 2018
by
aambazinga
427
views
theory-of-computation
decidability
co-turing-recognizable
1
vote
1
answer
209
TOC DECIDABILITY
Let E={<M>| M is a DFA that accepts some strings with more 1's than 0's} Show that E is decidable. How can E be decidable. How can a DFA compare between number of 1's and 0's. From the question I know that it's not talking about all, but some. The things is even some should not be decidable. isn't it?
aambazinga
asked
in
Theory of Computation
Sep 8, 2018
by
aambazinga
385
views
theory-of-computation
decidability
finite-automata
0
votes
1
answer
210
Difference between computability and decidability
Hi, Could someone please tell the difference between computability and decidability? Thanks
surbhijain93
asked
in
Theory of Computation
Sep 7, 2018
by
surbhijain93
2.6k
views
decidability
turing-machine
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