Regular Expressions

[Concentric]

If i need to create a regular expression for a language L that contains the letters {a,b} that if it contains the sub-string bb, it can only contain it once.Am i correct in saying that no string in L can contain more than 2 b's together.
Wouldn't bbb result in 2 sub-strings of bb: (bb)b and b(bb) and therefore not be allowed.

Thanks
@cguy hope you dont mind the ping

 

[XennoX]

Just so we're on the same page here:

* You have some string, say `bbb`.
* You're trying to find out whether a regular expression containing two b's would return two matches or not?

Well that depends on the settings of the engine you're using (or if I understand that you're creating).

Supplying the regex of `bb` against the string `bbb` results in the first two b's being matched and the 3rd b being ignored when I use the _pcre_ engine.

 

[Other Pineapple Smurf]

Some people, when confronted with a problem, think "I know, I'll use regular expressions." Now they have two problems.

OK, enough about my work email sig and answering your question ... It depends on your engine but you would use look ahead / look around to determine if it is 2 and not 3 b's.

https://www.regular-expressions.info/lookaround.html

Which language are you using and which engine?

 

[krycor]

Use to have this at work..

I actually like regular expressions and if you really want to feel pain do it in bash scripts to fix file naming conventions by finding, sorting + rename. Ah the good ole telecoms game of gazillion telecoms record files..