Knowledge Backfill and the Fat Comma
I remember reading something back in college where someone interviewed a lot of Unix folk to try to find the core set of knowledge to become a Unix Master, and found that there is none. Each person knows the things needed to do the things necessary for that person. The Novice can blow the mind of the Master.
I always try to look back, find the thing I should’ve learned but missed. There’s loads, and I always find more, especially when I jump into a new context. This time, I was reading a test.
The test created an object and used after from Class::Method::Modifiers to backfill an object.
It looked like after setup => sub { ... } and while I got the anonymous subroutine and what it did, I didn’t get after. (I anaologize it to the Neuralizer from Men In Black: Every time I look into it, I forget everything.) I asked a friend, and he mentioned a thing that I had been using forever and not thought about.
One thing I like about Perl is that it avoids operator overloading, like how + is addition or concatenation in Javascript, or many other things when used in array or object contexts, preferring variable overloading. + is and always will be addition, but with 'foo' + 2, it finds the best guess as to what 'foo' means mathematically, and brings it down to 0, so that becomes 2. If instead of 'foo' I used '29 Palms', it’ll return 31.
This goes onto arrays and hashes. Hashes are kinda arrays with an even number of entries, and you can swap keys and values by %hash = reverse %hash.
So that means …
my %x = ( 'a', 1, 'b', 2. );
%x = reverse %x;
say $json->encode( \%x );
# {
# "1" : "a",
# "2" : "b"
# }
The => or Fat Comma converts the thing before it as a string. I’ve used Perl forever, I’ve used hashes in Perl forever, so I’ve used this without thinking about it forever.
after setup => sub { ... } is just as easily after 'setup' , sub { ... }. I’m torn, personally, as to whether it makes the association any more clear. I mean, it feels like using a dispatch table, so it’s kinda cool.
I had been fairly Cargo Cult about this: I use the symbols (=>) and get the cargo ( hashes with bareword keys ) without thinking about how it happens. It just worked, and I went on. But know how it works and how I can use it in non-hash contexts, which I guess makes me…
say join ' ', Just => Another => Perl => Hacker => ;