Regex - Match 2 groups with same qualifier

Question

I would like to use regex to match following strings:

aba
ababaa
abababaaa
...

These strings follows the pattern :

(ab){1}(a){1}
(ab){2}(a}{2}
(ab){3}(a){3}
...

Is it possible to create a generic regex to much such pattern ( like (ab){n}(a){n} ) ?

See [How can we match a^n b^n?](https://stackoverflow.com/questions/3644266/) and [this regex demo](https://regex101.com/r/o37srh/1). — Wiktor Stribiżew, Feb 24 '21 at 11:49
Thanks, that's actually works! However it requires PCRE syntax support. Anyway i need it for my C++ program and boost::regex supports it. — Pafcio, Feb 24 '21 at 12:20

score 0 · Answer 1 · answered Feb 24 '21 at 11:40

0

Try using quantifiers

(ab)+(a)+

+ means 1 or more and * means 0 or more

answered Feb 24 '21 at 11:40

rhymefororange

The `(ab)+(a)+` pattern will also match `abaaaa`. – Wiktor Stribiżew Feb 24 '21 at 11:41
It shouldn't? I didn't get that from the question. Did you mean it should match 1 to 3 'a's in the end? – rhymefororange Feb 24 '21 at 11:46
No. It should match exactly same number of 'a's at the end as 'ab's at beginning. – Pafcio Feb 24 '21 at 11:50
Oh. Then my answer is incorrect, sorry. – rhymefororange Feb 24 '21 at 11:51

score 0 · Accepted Answer · answered Feb 24 '21 at 12:24

0

The answer was posted by Wiktor Stribiżew. Using PCRE syntax regex the solution is recursive pattern:

(ab(?1)?a)

answered Feb 24 '21 at 12:24

Pafcio

2 Answers2