Marcus Kazmierczak came up with a list of 10 one-liner examples that are meant to showcase Scala’s expressiveness . A [CoffeeScript version]http://ricardo.cc/2011/06/02/10-CoffeeScript-One-Liners-to-Impress-Your-Friends.html) quickly emerged, and now a Ruby one
Multiply each item in a list by 2
(1..10).map { |n| n * 2 }
Sum a list of numbers
(1..1000).inject { |sum, n| sum + n }
Or using the (built in) Symbol#to_proc syntax that’s been available since Ruby 1.8.7:
(1..1000).inject(&:+)
Or even just passing a symbol directly:
(1..1000).inject(:+)
Verify if tokens exist in a string
words = ["scala", "akka", "play framework", "sbt", "typesafe"]
tweet = "This is an example tweet talking about scala and sbt."
words.any? { |word| tweet.include?(word) }
Reading a file
file_text = File.read("data.txt")
file_lines = File.readlines("data.txt")
| The latter includes “\n” at the end of each element of the array, which can be trimmed by appending .map { | str | str.chop } or by using the alternative version: |
File.read("data.txt").split(/\n/)
Happy Birthday
4.times { |n| puts "Happy Birthday #{n==2 ? "dear Tony" : "to You"}" }
Filter a list of numbers
[49, 58, 76, 82, 88, 90].partition { |n| n > 60 }
Fetch and parse an XML web service
require 'open-uri'
require 'hpricot'
results = Hpricot(open("http://search.twitter.com/search.atom?&q=scala"))
This example requires open-uri and hpricot or equivalent libraries (you could use builtin ones if you wish). It’s not too much code, but Scala clearly wins here.
Find minimum (or maximum) in a list
[14, 35, -7, 46, 98].min [14, 35, -7, 46, 98].max
Parallel Processing
require 'parallel'
Parallel.map(lots_of_data) do |chunk|
heavy_computation(chunk)
end
Unlike Scala, multicore support is not built-in. It requires parallel or a similar gem.
Sieve of Eratosthenes
The Scala one liner is very clever, but entirely unreadable. A simpler implementation that is no longer a one-liner in Ruby would be:
index = 0
while primes[index]**2 <= primes.last
prime = primes[index]
primes = primes.select { |x| x == prime || x % prime != 0 }
index += 1
end
This last example is straight from StackOverflow . Not the prettiest code ever, but you get the idea.
-Matt