Idiosyncratic Ruby: Golfing Basics

Code Golf is the art of writing the shortest program possible. The less bytes the better. And the competition is just ridiculously strong! Head over to Anarchy Golf if you want to see more!

A good beginner's problem is printing out Pascal's Triangle: Spend a few days to get to 45 bytes. Spend a few months to get to 43 bytes!

Attention: A new golf course has opened at code.golf. Why not give it a try 😉?

10 Ruby Tricks You'll Learn by Playing Code Golf

While code golfing does not necessarily make you a better programmer, you can learn a lot about the programming language you are using. Here are some things that were new to me:

Dirty Interpolation

String interpolation (#{}) is sometimes possible without using curlies:

"You can directly interpolate #@instance variables, " \
"#@@class variables, and #$global variables!"

I must admit, this can confuse newcomers, but it looks fantastic!

Constant Assignment in Modifiers

It is perfectly legit to use assignments in conditions:

if a = 42
  p a
end
# => 42

However, this won't work with the shorter modifier syntax:

p b if b = 42
# NameError: undefined local variable or method `b'...

Unless… you use constants:

p C if C = 42
# => 42

Shebang `require`

What could possibly be shorter than:

require'json'; require 'yaml'
p JSON,YAML

It's inlined command-line options:

#!ruby -rjson -ryaml
p JSON,YAML

Iterating Input Lines

Finding the shortest way to read user input is a common problem for golfers and solutions vary, depending on how to process the input. My favorite one is to iterate over the input's lines:

$<.each{|e|p e}

Appending Output

puts and p are already good candidates to output content. However, sometimes, using << on STDOUT is a tiny bit (or byte) more efficient:

?a.upto(?z){|o|$><<o}

Regex Always Wins

This is one of the golden rules of golfing. Especially, combining the block syntax of gsub with the perlish regex variables can be very expressive!

"some_string".gsub(/(^|_)(\w)/){$2.upcase}

`String#tr`

However, it's not true - regexes do not always win. If you need to perform some simple character substitutions, tr is an extremely short (and also clean) way to do so:

# ROT13 Cipher
"Vqvbflapengvp Ehol".tr'a-zA-Z','n-za-mN-ZA-M'
# => "Idiosyncratic Ruby"

One More or Less

In some instances, you cannot use i+1 or i-1 without wrapping them in parenthesis. No problem, unary complement to the rescue:

-~42 # => 43
~-42 # => 41

Flexible Precedence

This is one of my favorites: Explicitly call (.) operators for alternative precedence semantics:

3*(2+1) #=> 9
3.*2+1 #=> 9

Quick Quit

What's a shorter way to quit a Ruby script than the 4 bytes long exit method?

1/0

Although this is longer than z (calling an undefined method), it's often easier to trigger programmatically.

Golfing Basics