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Questions related to formal languages, grammars, and automata theory

5 votes
1 answer
143 views

To what factor can I compress information from binary to Quinary

I am trying to think if we can have an injective mapping $\mathcal{f}$, say something like $\Sigma_{bool}= \{0,1\}^* $ to $\Sigma_{5} = \{0,1,2,3,4\}^* $ such that $|x| \leq 2.|\mathcal{f}(x)|$ The m …
Subhayan's user avatar
  • 1,696
1 vote

How do I prove that Context Free languages have more memory than FSM

There's a small mistake in your question. The FSM (DFA or NFA) are machines that accept regular languages. the CFL is also a language. They are accepted by a machine called PDA (PushDown Automata …
Subhayan's user avatar
  • 1,696
0 votes

Prove or disprove whether L is regular

@Shaull's solution is perfect.. here's a slightly different version of it... try to see, that $L$ = $L_1 \cup L_2$ where $L_1 = \{ w \in \{0,1\}^* \mid |w|_0 \gt |w|_1 + 2\}$ $L_2 = \{ w \in …
Subhayan's user avatar
  • 1,696
1 vote

Class of a Language

For a language that is regular but not CF or CS, construct a DFA/NFA that accepts it convert it to a regular expression show that it can be represented as an union, intersection or concatenation of …
Subhayan's user avatar
  • 1,696
0 votes
2 answers
412 views

Equivalence of Context-Free-Grammar and Context-Free-Grammar in CNF

Given any Context-Free-Grammar, $G$, and another in Chomsky Normal Form, $G_c$, how can we check if both $G$ and $G_c$ generate the same language? One of the trivial ways I know of is to convert $G …
Subhayan's user avatar
  • 1,696
5 votes

Decide if L is regular or not and argue it. Trying to use Pumping Lemma

(a): Recall that regular languages are closed under complement, i.e if $L$ is regular, so is $L'$. ($F_{L'} = Q_L- F_L$) Assume that $L$ is regular. This follows: if $L = \{x \in \{0,1\}^* \mid |x|_0 …
Subhayan's user avatar
  • 1,696
0 votes

What does the language {a, b, c}* exactly mean? How will the automaton for this look like?

It means this Language can 'generate' any string using the alphabets $a, b, c$, including the empty string $\epsilon$ There is no bound on the length of the string generated. Here's a NFA that acce …
Subhayan's user avatar
  • 1,696
3 votes
Accepted

Regular Expression as basis for creating this grammar

$A \rightarrow ba \mid A \mid B \mid cA$ under this $bababaccc$ is also legal You could try something like this... $S \rightarrow cS|cA$ $A \rightarrow baA|B$ $B \rightarrow bb$
Subhayan's user avatar
  • 1,696
1 vote
Accepted

Can a Turing Machine decide only non-regular languages?

@Karolis Juodele already gave the answer, and your answer is also correct. Another thing to keep in mind is although infinite languages can be undecidable, some of them are regular.. ex. $\{0\}^* \su …
Subhayan's user avatar
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