Beefy Boxes and Bandwidth Generously Provided by pair Networks
Do you know where your variables are?
 
PerlMonks  

Re^3: RegEx related line split

by JavaFan (Canon)
on Nov 14, 2011 at 11:41 UTC ( #937925=note: print w/ replies, xml ) Need Help??


in reply to Re^2: RegEx related line split
in thread RegEx related line split

Do you understand foo|bar? Do you understand $? Do you understand (?= )? Combine all three and you get (?=$|MARK).


Comment on Re^3: RegEx related line split
Select or Download Code
Re^4: RegEx related line split
by remiah (Hermit) on Nov 14, 2011 at 12:40 UTC
    Try to explain myself.

    foo|bar is foo or bar. if it is grouped by (foo|bar), the matched $1 will be set to "foo" or "bar".

    In this case ... it is not "non capturing grouping" (?foo|bar), because it is zero width look ahead assertion '(?='. Zero width look ahead assertion works like place holder and it does not eat up pos($expr) in matching.

    $ is the end of line... as far as I know.

    Well, it says look ahead for "end of line" or MARK and match against them as 'place holder'. I think I understand this!

    #!/usr/bin/perl use strict; use warnings; my $RefLine = "(a) This is first line(once all 4 was one line). (b) Th +is is second line; ( print "original -----\n"; print "$RefLine\n"; print "original -----\n\n"; print "\n## without 'end of line or' condtion. last line fails\n"; while( $RefLine =~ /(\([a-z]\).*?)(?=\([a-z]\))/g ){ my $p=pos $RefLine; print "$-[0], $p,matched=$&\n"; print "---\n"; } print "\n## without lookahead assertion... \n"; while( $RefLine =~ /(\([a-z]\).*?)($|\([a-z]\))/g ){ my $p=pos $RefLine; print "$-[0], $p,matched=$&\n"; print "---\n"; } print "\n## with 'end of line or' condtion and zero width place holder +\n"; while( $RefLine =~ /(\([a-z]\).*?)(?=$|\([a-z]\))/g ){ my $p=pos $RefLine; print "$-[0], $p,matched=$&\n"; print "---\n"; }

    Thank you very much JavaFan.

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://937925]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others meditating upon the Monastery: (21)
As of 2015-07-06 18:10 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    The top three priorities of my open tasks are (in descending order of likelihood to be worked on) ...









    Results (80 votes), past polls