Questions about the formal languages that can be described by regular expressions (in the sense of Kleene), or, equivalently, the languages that can be accepted by finite automata.

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6
votes
2answers
271 views

Generating all instances of a regular language up to a certain length

Given a fixed regular language R, what is the complexity of generating all members of R with length at most $n$? Suppose some reasonable model (RAM with $n$-bit words?) and a write-only output tape. ...
4
votes
1answer
210 views

What is an unambiguous language in the sense of Schützenberger?

I'm reading Thomas Wilke's survey on the connections between Temporal Logic and finite automata, finite semigroups and first-order logic. In Theorem 6 (by Kamp), the fragment ...
4
votes
6answers
1k views

What are regular expressions good for?

If you ask a question about parsing HTML with regex, you will certainly be referenced to this famous rant. Though there is not a canonical rant for it, I've also been told that regex aren't powerful ...
0
votes
0answers
201 views

algorithm that can determine for every regular language L [closed]

can you please tell me how can I show that there exists an algorithm that can determine for every regular language L, whether or not |L| ≥ 5
17
votes
5answers
713 views

Ambiguity and Logic

In automata theory (finite automata, pushdown automata, ...) and in complexity, there is a notion of "ambiguity". An automaton is ambiguous if there is a word $w$ with at least two distinct accepting ...
18
votes
5answers
1k views

A special class of languages: “circular” languages. Is it known?

Define the following class of "circular" languages over a finite alphabet Sigma. Actually, the name already exists to denote a different thing it seems, used in the field of DNA computing. AFAICT, ...
8
votes
2answers
2k views

Is JSON a Regular Language?

I was wondering if the JSON spec defined a regular language. It seems simple enough, but I'm not sure how to prove it myself. The reason I ask, is because I was wondering if one could use regular ...