Linked Questions

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1answer
16k views

Is this language regular or non-regular: {ww : w ∈ {a,b}* } [duplicate]

This is a question from a text book that's giving me some trouble. The question is: Determine whether or not this language is regular. Justify your answer. $$L = \{ww : w \in \{a,b\}^* \}$$ I ...
3
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1answer
7k views

Show that a language consisting of strings of a prime number of 1s is irregular using pumping lemma [duplicate]

Question: L is a language defined as $\ L = \{1^l | l\in primes\}$ (strings of 1s having a prime length). Show that this is not a regular language ($\ L \notin REG$). You may either use the theory ...
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1answer
7k views

Proof that {$a^m b^n$ | m!=n} is not regular [duplicate]

I know that the language $\{a^m b^n | n\neq m\}$ satisfies the pumping lemma, but it's still not regular (I have to count the # of a's and b's). How can I formally prove it?
2
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1answer
3k views

Proving that {0^{2^k}} is not regular with the Myhill-Nerode theorem [duplicate]

My language is the repetition of 0 to a length that's a power of 2: $L = \{ 0^k \ni k=2^n, n \geq 1 \}$ I want to know how to prove that this language is not regular. I have attempted the proof ...
2
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2answers
2k views

Prove that the following language is not regular: $\{0^i1^j : i \neq j\}$ [duplicate]

I was trying to approach this proof, after multiple reads and attempts I am getting nowhere. If someone could help me out that would be great. Should I use the pumping lemma, if so how show I start, ...
0
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1answer
1k views

Union of finite and non-regular language [duplicate]

Question: ($B$ and $C$ are languages) $B$ is finite,$C$ isn't regular: Prove/Disprove: $C\cup B$ isn't regular. Thoughts: My intuition says this is true, but I need an idea to prove it. Since I don'...
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1answer
2k views

Prove that the language L = {a^(m+n) b^m a^n | m, n ≥ 0} ∪ {a^m b^n a^(m+n) | m, n ≥ 0} is not regular [duplicate]

In general, how can we go about proving that union of two languages as non regular. In this case, the individual languages can be proved as non regular using pumping lemma. How can we apply pumping ...
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2answers
1k views

Prove or disprove whether L is regular [duplicate]

Let $\Sigma = \{0,1\}$. For every word $w \in \Sigma^*$, let $|w|_0$ and $|w|_1$ denote the count of 0's and 1's, respectively, in $w$. Let $L$ be the language $$L = \{ w \in \Sigma^* \mid |w|_0 \gt |...
1
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1answer
1k views

Proving a language is not regular [duplicate]

I need to prove that the following language is not regular $\{c^mb^na^n \mid n>0,m\geq0\}$ But I am not sure how to do that for this particular one. I vaguely understand pumping lemma, but ...
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1answer
1k views

pumping lemma for $L=\{a^n b^m c^k \mid n = m \vee m\neq k\}$ [duplicate]

Using pumping lemma, how can I prove that $L=\{a^n b^m c^k \mid n = m \vee m\neq k\}$ is not regular?. If I choose $w= a^m b^m c^m$ and pump up with $i=2$, if have $a^m=1 b^m c^m$ but the string is ...
2
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2answers
728 views

L ={ $a^{m^n}$ | $m$>$n$ } is Regular or not by pumping Lemma [duplicate]

L ={ $a^{m^n}$ | $m$>$n$ } I am bit confuse whether to consider this language as L = $(a^{m})^{n}$ OR L = $a^{\left(m^n\right)}$. If it is considered as L = $(a^m)^{n}$ then want to check it ...
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1answer
1k views

Pumping lemma on {a^n | n=3^k} — help finishing the proof [duplicate]

I am working on a pumping lemma question and trying to prove that the following is not regular, but I can't finish the proof, if someone can help me it will be great. So I am given this language: $L ...
1
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1answer
446 views

Non-regular Languages? [duplicate]

Possible Duplicate: How to prove that a language is not regular? Why $L_a$ and $L_b$ are not reguluar? $L_a = \{ e^i f^{n-i} g^j h^{n-j} : n \in N, 1 \leq i, j \leq n \}$. $L_b= \{nm^{i_1} ...
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votes
2answers
343 views

Finding nfa or dfa for a language [duplicate]

I'm trying to study for the summer ahead of class I saw this question, please how do I go about it? Find NFA/DFA for the language $L = \{0^n1^n : n \in N\}$
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1answer
774 views

Proving that a language given by a CFG is not regular [duplicate]

Consider the language defined by the following grammar: $$ \begin{align*} &S \rightarrow E \\ &S \rightarrow \epsilon \\ &E \rightarrow E+E \\ &E \rightarrow E-E \\ &E \rightarrow \...

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