Beefy Boxes and Bandwidth Generously Provided by pair Networks
laziness, impatience, and hubris
 
PerlMonks  

Re: A Regex simple Question

by Sidhekin (Priest)
on Sep 06, 2007 at 15:54 UTC ( #637464=note: print w/ replies, xml ) Need Help??


in reply to A Regex simple Question

Negative lookahead is always tricky ... you're on the right track though.

In this specific case you could do this:

/^a(?!b)(?:(?!ab).)+b$/

... or even this:

/^(?!.*ab)a.+b$/

... unless I've read you wrong, and you want to allow the string "ab" and even "ab000b"/"a000ab" (since the "ab" is not strictly between the "a" and the "b"), in which case you want this:

/^a(?:(?!ab.).)*b$/

... or even this:

/^(?!.+ab.)a.*b$/

Always tricky, the negative lookahead ... if you can split it, like FunkyMonk suggests (or some variation thereof), it'll be far more readable.

print "Just another Perl ${\(trickster and hacker)},"
The Sidhekin proves Sidhe did it!


Comment on Re: A Regex simple Question
Select or Download Code

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://637464]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others making s'mores by the fire in the courtyard of the Monastery: (15)
As of 2014-10-01 17:20 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    What is your favourite meta-syntactic variable name?














    Results (30 votes), past polls