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Questions related to formal languages, grammars, and automata theory

4 votes
3 answers
2k views

Definition of Turing Machine as a language acceptor

The following is an excerpt from the book "An Introduction to Formal Languages and Automata" by Peter Linz. My question is, why is $\Sigma^+$ used and not $\Sigma^\ast$?
Manu Thakur's user avatar
2 votes
1 answer
107 views

Find the grammar for the given language

$L = \{ w: |w| \bmod 3 \geq |w| \bmod 2 \}$ I know, when the length of strings is not $3, 9, 15, 21,\dots,$ they will be members of the given language but unable to write a grammar for this language …
Manu Thakur's user avatar
0 votes
1 answer
1k views

Find the Context Free Grammar

Let $\Sigma = \{a, b\}$. For each of the following languages, find a grammar that generates it. (a) $L_1 = \{a^n b^m : n\geq 0, m>n\}$ (b) $L_1^3$ (C) $L_1^*$ I know the grammar for the language $ …
Manu Thakur's user avatar