Re^3: split/map weirdness: empty strings vs undef

You can avoid that behaviour by using a capturing pattern.

$ perl -le'print join " : ", split /(\|)/, "2|3|||||"'
2 : | : 3 : | :  : | :  : | :  : | :  : |
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This is also documented in perldoc -f split. Of course now every other element is the separator, which isn't what we wanted. So out with them:

$ perl -le'print join " : ", grep ++$i%2, split /(\|)/, "2|3|||||"'
2 : 3 : : : :
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There you go.

Update: Yikes! I caught a mistake: the last field still disappears if empty. Count the pipes in the string and the colons in the output.. At this point we lose some grace.. The oneliner is ugly:

$ perl -le'print(join(" : ", grep(++$i%2, split /(\|)/, "2|3|||||"), (
+"")x(1-$i%2)))'
2 : 3 : : : : :
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while the multiliner is awkward:

$ perl -le'my @field = grep ++$i%2, split /(\|)/, "2|3|||||"; push @fi
+eld, "" unless $i%2; print @field'
2 : 3 : : : : :
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Oh well.

Makeshifts last the longest.

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Re: Re^3: split/map weirdness: empty strings vs undef by hossman (Prior) on Oct 04, 2002 at 22:34 UTC
That is damn elegant. UPDATE: After reading your update, i was a little dissapointed that i wouldn't be able to use your clean little trick, untill I looked at my data some more. Unlike ever other "seperated" data format I've ever seen, it allways puts a trailing seperator after the last field -- which means your orriginal one liner will work perfect for me ...I *need* to ignore the last pipe go figure	[reply]
Re^5: split/map weirdness: empty strings vs undef by Aristotle (Chancellor) on Oct 05, 2002 at 18:01 UTC
You know, that gives me another idea for the cases you need to conserve the last field, although it is so similar to the add a bogus field approach that it bears the question whether the capture/grep hoopla is worth the hassle if you went that route anyway: add a field separator to the string. `$ perl -le'$_ = "2\|3\|\|\|\|\|"; print join " : ", grep ++$i%2, split /(\\|) +/, "$_\|"' 2 : 3 : : : : :` [download] Makeshifts last the longest.	[reply] [d/l]