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Results tagged with regular-expressions
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user 54078
Questions about regular expressions, a formalism to describe regular languages.
4
votes
regular expression of star-height 1
The language has star-height 2. Note that the language includes
$R_0=(ba^+ba^+)^*$, but is disjoint from $R_1=(ba^+ba^+)^*ba^+$. Therefore, it suffices to show:
Claim: If $L$ has star-height 1 and $R …
- 361
2
votes
Regular expressions and semi-linear sets
The claim fails for two symbols. The Parikh image $M\subseteq \mathbb{N}\times\mathbb{N}$ of $(abb^*)^*$ is not linear:
It is easy to see that for every finitely generated submonoid $N$ of $M$, there …
- 361