RegEx related line split

dominic01 has asked for the wisdom of the Perl Monks concerning the following question:

Replies are listed 'Best First'.
Re: RegEx related line split by johngg (Canon) on Nov 11, 2011 at 17:59 UTC
This might be what you want. `knoppix@Microknoppix:~$ perl -E ' > $line = q{(a) Line 1. (b) Line 2. (c) Line 32. (d) Line 42.}; > @arr = split m{(?=$[a-z]$)}, $line; > say qq{>$_<} for @arr;' >(a) Line 1. < >(b) Line 2. < >(c) Line 32. < >(d) Line 42.< knoppix@Microknoppix:~$` [download] I hope this is of use. Cheers, JohnGG	[reply] [d/l]
Re^2: RegEx related line split by dominic01 (Sexton) on Nov 14, 2011 at 03:13 UTC
Thank you. This works as per my requirement but I was trying one other pattern `$line = q{a) Line 1. b) Line 2. c) Line 32. d) Line 42.};` [download] Here it matches if some (words) within () that are coming in the line.	[reply] [d/l]
Re^3: RegEx related line split by johngg (Canon) on Nov 14, 2011 at 10:30 UTC
Do you mean that the opening parenthesis is optional in the text you are spliting? If so, you can use a '`?`' quantifier to make the opening parenthesis "zero or one of" but you also have to use a negative look behind to make sure you don't split '(' from 'a)'. I've added the '`x`' modifier to the pattern so I can space it out and make it more readable. `knoppix@Microknoppix:~$ perl -E ' > $line = q{(a) Line 1. b) Line 2. (c) Line 32. d) Line 42.}; > @arr = split m{ (?<! $ ) (?= \(? [a-z] $ ) }x, $line; > say qq{>$_<} for @arr;' >(a) Line 1. < >b) Line 2. < >(c) Line 32. < >d) Line 42.< knoppix@Microknoppix:~$` [download] I hope this is helpful. Cheers, JohnGG	[reply] [d/l] [select]
Re^2: RegEx related line split by johngg (Canon) on Nov 14, 2011 at 10:27 UTC
Do you mean that the opening parenthesis is optional in the text you are spliting? If so, you can use a '`?`' quantifier to make the opening parenthesis "zero or one of" but you also have to use a negative look behind to make sure you don't split '(' from 'a)'. I've added the '`x`' modifier to the pattern so I can space it out and make it more readable. `knoppix@Microknoppix:~$ perl -E ' > $line = q{(a) Line 1. b) Line 2. (c) Line 32. d) Line 42.}; > @arr = split m{ (?<! $ ) (?= \(? [a-z] $ ) }x, $line; > say qq{>$_<} for @arr;' >(a) Line 1. < >b) Line 2. < >(c) Line 32. < >d) Line 42.< knoppix@Microknoppix:~$` [download] I hope this is helpful. Update: Oops, looks like I replied to myself rather than the OP's subsequent question. Please ignore this and consider my reply to him. Cheers, JohnGG	[reply] [d/l] [select]
Re^3: RegEx related line split by Gavin (Archbishop) on Nov 14, 2011 at 10:41 UTC
Alas a senior moment, it happens to all old coders.	[reply]
Re: RegEx related line split by Lotus1 (Vicar) on Nov 11, 2011 at 21:58 UTC
You only had two capturing ()'s so $3 won't return anything your way. The `.+` captures everything up to (d) since it is greedy. To make your regex work: Use the /g option. Remove the ^ anchor at the start. Remove the (.?) at the end. Add the $ option at the end in place of the a-z in the lookahead. `my $RefLine = "(a) This is first line. (b) This is second line; (c) Th +is is different line 32. (d) Here is the last line."; @lines = $RefLine =~ /($[a-z]$.?)(?=$\|$[a-z]$)/g; print ">>$_<<\n" foreach @lines;` [download]	[reply] [d/l] [select]
Re^2: RegEx related line split by dominic01 (Sexton) on Nov 14, 2011 at 03:17 UTC
This is great. Thank You.	[reply]
Re^2: RegEx related line split by remiah (Hermit) on Nov 14, 2011 at 08:54 UTC
Would you mind if I ask my question? I don't understand "$ option" and saw perlre's Extended Patterns, but I could not figure out what is this. `(?=$\|MARK)` [download] "(?=" is zero width look ahead assertion and I wonder what is "$\|" ? Usually I will do this with character class `@lines = $RefLine =~ /($[a-z]$[^\(])/g;` [download] This will fail if $RefLine includes another (). `my $RefLine = "(a) This is first line(once all 4 lines were one line). + (b) This is second line; ( c) This is different line 32. (d) Here is the last line.";` [download] But your's works fine. More robust. I am glad with some pointer or clue for me. regards.	[reply] [d/l] [select]
Re^3: RegEx related line split by JavaFan (Canon) on Nov 14, 2011 at 11:41 UTC
Do you understand `foo\|bar`? Do you understand `$`? Do you understand `(?= )`? Combine all three and you get `(?=$\|MARK)`.	[reply] [d/l] [select]
Re^4: RegEx related line split by remiah (Hermit) on Nov 14, 2011 at 12:40 UTC