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Re: 10 Perl One Liners to Impress(?) Your Friends

Evan Carroll — Mon, 06 Jun 2011 18:07:36 -0000

the fastest thing is to set the hash value to undef which doesn't have ref counting, and is an internal pointer to SV_UNDEF, and to use exists(). However, that's reasonably more ugly. And, the point is you can at least stay O(n) with a hash, non-set array intersections are always O(n**2) which gets bad fast.

You can use all of the suggestions, also this rule is universal. One loop is always better.

Not:
say for grep { $tweet =~ /\b$_\b/ } @wordlist;

But:
for (@wordlist) { say if /\b$_\b/ }

Re: 10 Perl One Liners to Impress(?) Your Friends

rjh29 — Sun, 05 Jun 2011 20:16:32 -0000

I used map because it's a direct analog to the Scala solution in the original article - then tacked a 'say for' at the beginning and didn't think about it. D'oh! Same deal with using smart-match rather than a hash lookup (because other languages have an 'in' operator). Thanks, though! Do you mind if I add your improvements to the article?

Btw, checking 'exists $tweet_words{$_}' seems to be about 5-10% faster than not using exists on my machine (Perl 5.10.1 on Ubuntu 10.04).

Re: 10 Perl One Liners to Impress(?) Your Friends

Evan Carroll — Sun, 05 Jun 2011 13:04:30 -0000

Most of these aren't one liners, they're just expressions. Most of them can also be written better...

Here you're iterating twice for no reason..
perl -E 'say for map { $_ * 2 } 1..10'
Just do, -E'say $_*2 for 1..10'

Your algo for checking if a word exists in a string is slow. If one liners don't matter...
my %tweet_words;
$tweet_words{$_}=1 for split /\W/, $tweet;
say $tweet_words ? "found [$_]" : "not found [$_"] for @wordlist;

List::Util is nice, but for one liners this will achive the same effect.
perl -00E'my $foo = <>; print $foo' foobar.txt

Again, you seem to be hellset on using `for` and `map`... you should pick.
say for map { "Happy Birthday to " . ($_ == 2 ? "dear Name" : "you") } 0..3;
say "Happy Birthday to " . ($_ == 2 ? "dear Name" : "you") for 0..3;

Re: 10 Perl One Liners to Impress(?) Your Friends

Craig DeForest — Sun, 05 Jun 2011 09:23:09 -0000

It's interesting that so many of your examples are numeric but you haven't tried "use PDL;", which loads a scientific grade numerical processing package. PDL minmax is between 30 and 150 times faster than List::MoreUtils::minmax (it gets the gain by working on traditional structured arrays of numbers rather than on Perl lists of polymorphous scalars).