Variables: Declared? Defined? Both??
I've put forth some effort recently towards exploring some other Perl-ish but not-Perl scripting languages to (I hope) reinforce my resume. I love Perl but if I hope to become a real professional with my programming then I think it behooves me to branch out a bit. I haven't strayed far from Perl however as the languages that have intrigued me the most so far have been Raku and Javascript.
What is or isn't “Perl-ish” I suppose is subjective but I think these two have a syntax I can find some familiarity with. I still haven't felt empowered enough yet to really want to use either of these for actual $workStuff yet. Oddly enough I've reached for another Perl-ish language for this that I initially only cared about for its killer app.
If there's one thing that kinda struck me as odd about Ruby it's how variables are “defined.” Honestly I have a tendancy to spend hours of trial an error when learning new things to spare me the ten minutes it takes to just read the documentation but I got to thinking about it and realized I had a knowledge gap in what makes a variable “defined”? If I declare a variable like so:
$ re.pl
$ my $string = 'ayy... lmao';
I've declared and defined the variable. But there's this other thing I've been doing without ever giving it much thought:
$ my ($string, %hash, @list);
So I just defined 3 different variables at once right? Turns out that is not the case as I learned in, of all things, a JS tutorial. I've declared these three variables but they are infact, undefined:
$ node
Welcome to Node.js v14.17.0.
Type ".help" for more information.
> let string, hash, list;
undefined
> string
undefined
> undeclaredVar
Uncaught ReferenceError: undeclaredVar is not defined
I recognized this as undef in Perl:
$ re.pl
$ my ($string, %hash, @list);
$ use Data::Dumper;
$ Dumper($string);
$VAR1 = undef;
Cool. So there's declared variables and then there's defined variables. But the thing about Ruby is there's no let or my keywords. The way you define a variable in Ruby reminds me more of bash:
$ irb
irb(main):001:0> string = 'ayy... lmao'
=> "ayy... lmao"
But what if I just want to “declare” a variable but not “define” it? The best solution I've found so far goes like this:
irb(main):001:0> string = nil
=> nil
This is actually different than:
irb(main):001:0> string = ''
=> ""
Coincidentally (or perhaps not, I'm using a filler word) only false and nil will evaluate as false in Ruby:
irb(main):001:0> string = ''
=> ""
irb(main):002:0> puts "ayy... lmao" if string
ayy... lmao
=> nil
That means this madness is real:
irb(main):003:0> puts "ayy... lmao" if 0
ayy... lmao
=> nil
If only Ruby had let or my so I could declare but not define variables... Wait. What if I did something like... ?:
irb(main):001:0> string, hash, list = nil
=> nil
irb(main):002:0> puts "ayy... lmao" if list
=> nil
irb(main):003:0> puts "ayy... lmao" if undeclaredVar
(irb):3:in `<main>': undefined local variable or method `undeclaredVar' for main:Object (NameError)
from /usr/share/gems/gems/irb-1.3.5/exe/irb:11:in `<top (required)>'
from /usr/bin/irb:23:in `load'
from /usr/bin/irb:23:in `<main>'
Ultimately it seems Ruby gives me all the roap I need to hang myself. It just doesn't look right to me because I've grown fond of let and/or my. One could write their entire web backend and frontend both in JS but I'd rather use Ruby on Rails in my backend. Or in theory at least. I learned Ruby to learn Rails but I can't yet write anything useful with Rails. But with plain Ruby I can do some neat system-side stuff as I would with Perl. My homepage uses Perl on the backend because I already knew how to do it with Perl. And my frontend is more JS than CSS because I actually like JS the more I learn about it.
But I really need to stop dicking around and learn Rails already. I wrote a blog post for the first time in months to put off reading another chapter of my Rails book. On the brightside I won't have to learn SQL if I can master ActiveRecord. How nice would it be to just do everything in one language? SQL (pronounced like sequel) must be a conspiracy to sell more CS degrees. Or Oracle licenses.
I should probably just learn SQL so I can finally learn Rails.
Dan B