perlish way of splitting file records

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

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Re: perlish way of splitting file records by davorg (Chancellor) on Jun 01, 2006 at 15:46 UTC
You were very close. You need a list slice. `$result = (split /:/, <FILEHANDLE>)[3];` [download] -- <http://dave.org.uk> "The first rule of Perl club is you do not talk about Perl club." -- Chip Salzenberg	[reply] [d/l]
Re: perlish way of splitting file records by state-o-dis-array (Hermit) on Jun 01, 2006 at 15:54 UTC
Is it always the fourth element you need or always the last? Consider: `(split(/:/,<FILEHANDLE>))[-1]` [download] If you always want the last element.	[reply] [d/l]
Re: perlish way of splitting file records by davido (Cardinal) on Jun 01, 2006 at 17:04 UTC
For a short list like yours it doesn't really matter. But for a really big string with lots of elements, it's wasteful to create a big list (which is a copy of the string but split up) only to grab the last element. ...think along the lines of photocopying a book, and throwing away the entire copy except the last page. Here's a method that uses a regexp to find only the last element in the string: `my $last_element; my $line = <FILEHANDLE>; if( $line =~ m/:([^:]*)\Z/ ) { $last_element = $1; }` [download] Dave	[reply] [d/l]
Re: perlish way of splitting file records by bpphillips (Friar) on Jun 01, 2006 at 15:58 UTC
you can also use an anonymous array to accomplish what you attempted in your second example: `print [ split(/:/,<FILEHANDLE>) ]->[3]` [download] Oddly enough, to use a list slice there are some subtle parenthesis issues: `# this works: print ((split /:/, <FILEHANDLE>)[3]); # doesn't work (note the missing outer parenthesis): print (split /:/, <FILEHANDLE>)[3];` [download] I'm guessing the second example has some ambiguity with taking the slice off the `print` or the `split` -- Brian Update: As pointed out below, an anonymous array is slower (by 39%) than a plain ol' list slice. Depending on the circumstances, however, it's very unlikely that this slowdown would ever be noticable (since on the box I tested, it was still able to perform 89,445 anonymous array creations and access per second).	[reply] [d/l] [select]
Re^2: perlish way of splitting file records by VSarkiss (Monsignor) on Jun 01, 2006 at 16:39 UTC
The parenthesis following `print` is assumed to contain its arguments. You can either enclose everything in parens as you've done, or disambiguate in some other way, such as with unary plus. Consider: `$ perl -MO=Deparse -e 'print ((split /:/,<FILEHANDLE>)[3])' print((split(/:/, <FILEHANDLE>, 0))[3]); -e syntax OK $ perl -MO=Deparse -e 'print +(split /:/,<FILEHANDLE>)[3]' print((split(/:/, <FILEHANDLE>, 0))[3]); -e syntax OK` [download] Do not rebuke them with harsh words ... but rather lead them gently - with URLs - so that they may learn wisdom.	[reply] [d/l] [select]
Re^2: perlish way of splitting file records by ikegami (Patriarch) on Jun 01, 2006 at 17:25 UTC
Yes, it's possible to use an anonymous array, but it's needlessly expensive when a list slice will do.	[reply]