Re: Re: A complex recursive regex,help


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Re: Re: A complex recursive regex,help

by OM_Zen (Scribe)

on Feb 06, 2003 at 18:53 UTC ( [id://233227]=note: print w/replies, xml )

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in reply to Re: A complex recursive regex,help
in thread A complex recursive regex,help

Hi Tachyon ,

      my $a = "x|xx|xx|xxxx|xx|xxx|xx|xx|x";
      $a =~ s/(?<=\|)xx(?=(\||$))/x x/g;

      # this is actually doing the regex edge cases too Tachyon
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Re: Re: Re: A complex recursive regex,help
by tachyon (Chancellor) on Feb 06, 2003 at 23:14 UTC

Well *actually* it does not. Your test string does not *actually* contain the edge cases ( xx at the begining and end of the string):o) If your test string had contained the edge cases you would no doubt have noted the following failure case.....

my $a = "xx|xx|xx|xxxx|xx|xxx|xx|xx|xx";
$a =~ s/(?<=\|)xx(?=(\||$))/x x/g;
print $a;
__DATA__
xx|x x|x x|xxxx|x x|xxx|x x|x x|x x
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Here is one way to fix your regex:

$a =~ s/(?<=\|)|^xx(?=(\||$))/x x/g;

# and here is a way using the zero width boundary assertion \b
# that will match | ^ or $ but also matches any non aphlanumeric 
# so would potentially fail on '|xx,xx|' type strings
# if they exist in practice as your real data is no doubt
# not really xx.....
$a =~ s/\bxx\b/x x/g;
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cheers

tachyon

s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print

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