Re^2: Delimited Backtracking with Regex


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Re^2: Delimited Backtracking with Regex

by ikegami (Patriarch)

on Apr 21, 2006 at 02:26 UTC ( [id://544760]=note: print w/replies, xml )

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in reply to Re: Delimited Backtracking with Regex
in thread Delimited Backtracking with Regex

I've been asked why I used a package variable instead of a lexical variable. It's because regexps close around the lexicals that exist when they are first run.

                                       # pass  1   2   3
                                       #      --- --- ---
sub test {
   my @matches;
   '' =~ /
      (?{ push @matches, 'a' })
      (?{ print(scalar(@matches), "\n") })   # 1   2   3
   /xg;  
   print(scalar(@matches), "\n");            # 1   0   0
}

test() for 1..3;
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A variable called @matches is created everytime test is called. The regexp always uses the variable from the first call.

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Re^3: Delimited Backtracking with Regex
by blokhead (Monsignor) on Apr 21, 2006 at 03:07 UTC

push

Re^3: Regexes: finding ALL matches (including overlap)

{
  my @matches;
  my $push = qr/(?{ push @matches, $1 })/;

  sub match_all_ways {
      my ($string, $regex) = @_;
      @matches = ();
      $string =~ m/($regex)$push(?!)/;
      return @matches;
  }
}

print match_all_ways( "TXXXABCDGXXXCCCDTGYYYCCCYYYCC", qr/XXX.*YYY/ );
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(?{push @matches, $1})

blokhead

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