67 questions linked to/from How to show that L = L(G)?
663 views

### Show that language generated by grammar is regular

We have grammar with nonterminals $X_1,...X_n$ terminals $V_t$ and rewriting rules of form: $X_i \rightarrow a \in V_t$ $X_i \rightarrow X_jX_k, \ i \ge j , \ i > k$ How can I show that ...
285 views

### Show that a language cannot be generated by linear grammar

I have a language $L= \{ w \in \{a,b\}^* ; |w|_b=2i, i \ge 0 \}$ that is a language with even number of b's. I found a grammar for it with these rules: $S \rightarrow aS \ | \ bL \ | \ \lambda$...
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### Finding the language generated for CFG

What language generated by the following context-free grammar 1) S------> SaS | b i already know the answer to question one but to prove it would is be something like this: S -----> SaaS -----> baab ...
257 views

### Proof of completeness for CFG having twice as many zeroes as ones [duplicate]

One possible CFG containing twice as many zeros as ones can be, S -> 0S0S1S | 0S1S0S | 1S0S0S | ϵ (This CFG is redundant but it will do the job. So I am not interested in the redundancy. Other ...
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### Design a grammar for this context-free language

I am doing an exercise from Models Of Computation - Ch - 5, Q-1(r). Design a grammar that generates this context-free language $\{ x\space\$\space y^R \,|\, x, y \in\{0, 1\}^* \text{ and } x \ne y\}...
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### How do I get and/or verify a formal Grammar for a given formal Language? [duplicate]

I was given the Language $L=\left \{ a^nb^na^nb^n |n\epsilon \mathbb{N} \right \}$ and I'm supposed to find a Grammar that generates that Language. After some trying and fiddling I found one that I ...
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### Why is the distinction between linear and context-free grammars useful?

The linear grammar is a grammar that's either left, right or left and right linear. The context-free grammar can contain any kind of productions of non-terminals and terminals. All linear grammars ...
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### Context-free grammar for“not-at-all” palindromes

I need to bulid a context-free grammar for $\qquad \mathscr{L_4}=\{w\in\{a,b,c\}^* \mid w\text{ is not palindrome at all}\}$ Not palindrom at all: We will say that a word $w$ is not palindrome at ...
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### Tools or techniques for studying the language a CFG produces? [duplicate]

When developing a CFG, I find that one can be confused about whether the grammar is correct, i.e. whether it recognizes only the required strings and not other strings. But this can be hard to see? ...
268 views

### Figuring out the language of a non-linear CFG

I have the CFG G with the following production rules: $$S \to aSaS \mid b$$ Is it possible to find $L(G)$? I have no idea how describe it by any pattern. I use grammophone to check example words, ...
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### What are resources that I can use to learn about formal langauges?

What are some good resources for practice problems on formal languages? Every textbook I've seen contains few practice problems with even fewer answers. I would like a resource that has questions with ...
279 views

### Why is this language not context free?

I been watching tutorials about how to check if a language is not context-free and in 1 video there was a language: L = {a^n b^n c^n | n ≥ 0} and they used a pumping lemma to prove that it's not ...
573 views

### Describe the language generated by a given context free grammar

I had an exercise: Describe the language generated by the following given context free grammar and prove it by induction. \begin{align} S &\to SA \mid \epsilon \\ A &\to aS \mid bA \...
I need to find a grammar that generates the language composed by all words that have more $a$ than $b$ given an alphabet $\{a,b\}$ I tried the following production rules: ...