Pretty much just the title. Is it all possible combinations of a and b that have 2 letters ?

  • 1
    $\begingroup$ Probably means $\{a,b\}^*\cdot \{a,b\}^*$ where $\cdot$ is the concatenation operation for languages. In this case, its not hard to show that $(\{a,b\}^*)^2=\{a,b\}^*$. $\endgroup$
    – nir shahar
    Nov 2, 2021 at 10:44
  • 1
    $\begingroup$ It could also mean pairs of words from $\{a,b\}^*$, e.g., $(abba,baaa)$. Depends on the context. $\endgroup$
    – Shaull
    Nov 2, 2021 at 11:17
  • $\begingroup$ Don't forget that the empty string, $\epsilon$ is, for example, contained in $\{a,b\}^*$ so $(\{a,b\}^*)^2$ would also include $\epsilon, a$ and $b$. $\endgroup$ Nov 2, 2021 at 15:36

1 Answer 1


It’s not a standard way to specify a regular or any other language, so any answer would be a guess. Most likely candidates:

A string in (a, b)*, followed by another string in (a, b)*

A string in (a, b)*, followed by the same string again. 

Ask whoever gave this specification for a language.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.