split and join, what's the clever way to do it

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

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Re: split and join, what's the clever way to do it by ikegami (Patriarch) on Jan 27, 2008 at 03:49 UTC
It's already been specified that specifying `split`'s 3rd argument is the solution. I just wanted to note the 3rd argument is also very useful to disable `split`'s default of removing trailing blank fields. `>perl -le"print join '\|', split /\\|/, '\|a\|b\|c\|\|'" \|a\|b\|c >perl -le"print join '\|', split /\\|/, '\|a\|b\|c\|\|', -1" \|a\|b\|c\|\|` [download] I've always wondered why `split` is lossy by default, especially since I rarely if ever need the lossy behaviour. Either I don't care since I shouldn't be getting blank fields, or I want to keep the blank fields.	[reply] [d/l] [select]
Re^2: split and join, what's the clever way to do it by cosmicperl (Chaplain) on Jan 30, 2008 at 18:06 UTC
And there was me thinking that the 3rd argument would mean ignoring any extra pipes. Thanks for all the info guys! Lyle	[reply]
Re: split and join, what's the clever way to do it by hipowls (Curate) on Jan 27, 2008 at 03:35 UTC
`my ($var1, $var2, $var3, $var4, $var5) = split /\\|/, $line, 5;` [download] See split Update: Changed split to use `/\\|/` instead of `'\|'`. Thanks for pointing it out.	[reply] [d/l] [select]
Re^2: split and join, what's the clever way to do it by ikegami (Patriarch) on Jan 27, 2008 at 03:55 UTC
You've introduced a bug. The first arg of `split` is a regex even if you obfuscate that fact by using quotes, so the `\|` needs to be escaped: `split '\|', $line, 5; # WRONG split '\\\|', $line, 5; # ok split /\\|/', $line, 5; # Better split qr/\\|/', $line, 5; # Can also use qr// split $re, $line, 5; # or compiled regexes` [download] Other useful syntaxes: `my @rec = = split /\\|/, $line, 5;` [download] `my %rec; @rec{qw( var1 var2 var3 var4 var5 )} = split /\\|/, $line, 5;` [download]	[reply] [d/l] [select]
Re^3: split and join, what's the clever way to do it by dsheroh (Monsignor) on Jan 27, 2008 at 18:25 UTC
Having been bitten by that myself, are there any documents explaining why `split` behaves this way rather than the (IMO more sensible) alternative of splitting on a regex if it's /specified as a regex/ and splitting on a plain string if it's 'specified as a plain string'?	[reply] [d/l]
Re^4: split and join, what's the clever way to do it by ikegami (Patriarch) on Jan 28, 2008 at 01:10 UTC
Re^4: split and join, what's the clever way to do it by ysth (Canon) on Jan 28, 2008 at 02:52 UTC
Re^2: split and join, what's the clever way to do it by Fletch (Bishop) on Jan 27, 2008 at 03:51 UTC
The first argument to split is a regex, not a string. It makes a difference. `$ perl -le '$line = "a\|b\|c\|d"; print "-- $_:\n", join( "\n", split( $_ +, $line ) ) for ( qr/\\|/, "\|" )' -- (?-xism:\\|): a b c d -- \|: a \| b \| c \| d` [download] The cake is a lie. The cake is a lie. The cake is a lie.	[reply] [d/l]
Re: split and join, what's the clever way to do it by pilcrow (Sexton) on Jan 30, 2008 at 18:20 UTC
`my @data = split(/\\|/, $line); my $var1 = unshift @line; my $var2 ... my $var5 = join @line;` [download] As an aside, surely `my $var1 = shift @data` was meant above. -Mike	[reply] [d/l]