Re^2: regex at word boundary

You're right, the (corrected) code won't find palindromes. It wasn't intended to. It was the first step in finding a palindrome candidate. After the candidate is found I can strip out spaces and check to see if the word group does qualify as a palindrome.

Ultimately I don't care about finding palindromes. It is just a little puzzle to apply some time to. Some people do soduko puzzles, some crosswords, I look for little problems that I don't know the answer to and explore the possibilities.

Be Appropriate && Follow Your Curiosity

Comment on Re^2: regex at word boundary

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Re^3: regex at word boundary by QM (Parson) on Dec 07, 2005 at 21:07 UTC
You're right, the (corrected) code won't find palindromes. It wasn't intended to. It was the first step in finding a palindrome candidate. OK, fair enough. So what did you want it to do? Did you just want to check for repeated characters at the proper end of word boundaries? [Insert "Lightbulb Over Head" graphic here ] You just want a filter to grab candidates, then strip whitespace, then test for palindrome-ness. I think you'd do us a favor by coming up with an appropriate regex with `??{code}`, something near: `/(\b (([a-z]) # at least one char ?{local @suffix; push @suffix, $^N}) # build up suffix (([a-z) ?{local @suffix; push @suffix, $^N} \| \S+)+ [a-z]? # possible odd char (([a-z]) (?{if ($^N eq $suffix[-1]) {pop @suffix}}) \| \S+)+) (([a-z]) (?{if ($^N eq $suffix[-1]) {pop @suffix}}) \b) /x` [download] Though I don't think that works, and it's untested. (Hey, I have to leave something up to you.) Besides, there's a lot left out of the perlre with `?{code}` and `??{code}`, so please come back and tell us what it should say :) -QM -- Quantum Mechanics: The dreams stuff is made of	[reply] [d/l] [select]

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Re^3: regex at word boundary
by QM (Parson) on Dec 07, 2005 at 21:07 UTC

You're right, the (corrected) code won't find palindromes. It wasn't intended to. It was the first step in finding a palindrome candidate.

[Insert "Lightbulb Over Head" graphic here ]

You just want a filter to grab candidates, then strip whitespace, then test for palindrome-ness.

I think you'd do us a favor by coming up with an appropriate regex with ??{code}, something near:

/(\b
  (([a-z])                        # at least one char
   ?{local @suffix; push @suffix, $^N}) # build up suffix
  (([a-z)
   ?{local @suffix; push @suffix, $^N}
   | \S+)+
  [a-z]?                             # possible odd char
  (([a-z])
   (?{if ($^N eq $suffix[-1]) {pop @suffix}})
   | \S+)+)
  (([a-z])
   (?{if ($^N eq $suffix[-1]) {pop @suffix}})
 \b)
/x
[download]

perlre

?{code}

??{code}

-QM
--
Quantum Mechanics: The dreams stuff is made of

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