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Results tagged with regular-languages
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user 71238
Questions about properties of the class of regular languages and individual languages.
2
votes
Accepted
DFAs are regular languages, but regular languages are closed under concatenation
The third paragraph is the correct description how to interpret the statement from your notes. This is also easy to prove: Say $L$ and $L'$ are regular languages described by some regular expressions …
- 1,536
3
votes
How to understand and apply pumping lemma to prove $a^{i+1} b^{4i+2}$ is not regular?
Since I see questions about the pumping lemma on this site quite often, I decided to write a bit of a longer answer hoping that it helps people "get" the PL rather than just treating it as a "plug-n-c …
- 1,536
1
vote
Accepted
Deterministic infinite automaton equals a normal DFA?
That approach indeed works. It is well known that $L = \{a^n b^n \mid n \in \mathbb N\}$ is not regular and hence not recognized by any "normal" DFA, so it suffices to show that $L$ can be recognized …
- 1,536
3
votes
Accepted
What is the the pumping length for the regular expression (0+0001)((1111)*+(00)*)
It will be convenient to distribute the concatenation to get the equivalent RE
$$0(1111)^\ast + 0(00)^\ast + 0001(1111)^\ast + 0001(00)^\ast.$$
Now note that any such string can be writen as $s = s_i …
- 1,536
1
vote
Constructing a NFA from a regular expression
Your solution is nearly correct, however you need to remove the $c$-transition of $S_0$ and the $a$-transition from $S_0$ to $S_2$ and add a new state, say $S_3$, which is reached from $S_0$ via an $\ …
- 1,536