I'm not really sure what the real value of rosettacode.org is, but while looking at implementations for continued fractions in C++, my mind wandered down to the Perl 6 section and was sucked into a black hole:
Perl6 allows us to define a custom composition operator. We can then use it with the triangular reduction metaoperator, and map each resulting function with an infinite value for x.I program a fair amount in Perl 5 and I don't recognize a thing here. I remember seeing a bit of an interview of Larry Wall, and he was talking about how much fun he was having posting code to rosettacode.org. I'm going to blame this one on him.sub infix:<⚬>(&f, &g) { -> $x { &f(&g($x)) } }
sub continued-fraction(@a, @b) { [\⚬] map { @a[$_] + @b[$_] / * }, 0 .. * }
Labels: perl
While we eventually want to get to test first design, we're not there right now. But that doesn't mean I can't do anything. Usually its just proving out an idea, like this,
Perl is not the language that most people think of when designing an application. Sure it can scrape web logs and turn X into Y in one line of code (where X and Y can be almost anything if you're Randall Schwartz), but beyond that its not used for much.
If you get in any further than a couple line script, perl just gets scary. Like today, my friend who aspires to greatness asked me if @$yy{key} was different than @{$yy{key}}.
The short answer is yes.
The long answer is that the first is an array slice dereferencing an anonymous hash in the scalar $yy. The second is dereferencing an anonymous array in the hash %yy under the key 'key'.
Perl lets you build so many layers of collections and lists that you just find yourself building these elaborate structures because they fit the data or how you want to use it. Pretty soon you're doing,
@{$res{$_->{channel_id}}{$_->{key_type}}[$k]}{qw(count z)}= @$_{qw(ct z)}
And thinking nothing of it. Ok, maybe you have to think about it a little bit because you get it wrong the first time, but a quick splash of Data::Dumper() and all is revealed.
