10 Ruby One Liners to Impress Your Friends

gistfile1.rb

#10 Ruby One Liners to Impress Your Friends
#http://programmingzen.com/2011/06/02/10-ruby-one-liners-to-impress-your-friends/

#1. Multiply each item in a list by 2

p (1..10).map {|n| n*2} 

#2.Sum a list of numbers

p (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:

p (1..1000).inject(&:+)

#Or even just passing a symbol directly: 

p (1..1000).inject(:+)

#3. 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."

p words.any? { |word| tweet.include?(word) } 

#4. Reading a file

p file_text = File.read("data.txt")
p 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:

p File.read("data.txt").split(/\n/)   

#5. Happy Birthday

4.times { |n| puts "Happy Birthday #{n==2 ? "dear Tony" : "to You"}" }

#6. Filter a list of numbers

p [49, 58, 76, 82, 88, 90].partition { |n| n > 60 } 

#7.Fetch and parse an XML web service

require 'rubygems'  
require 'open-uri'
require 'hpricot'

results = Hpricot(open("http://www.google.com/search?q=ruby"))
#p results

#8.Find minimum (or maximum) in a list

p [14, 35, -7, 46, 98].min
p [14, 35, -7, 46, 98].max

#9. Parallel Processing

require 'rubygems' 
require 'parallel'

Parallel.map(lots_of_data) do |chunk|
  heavy_computation(chunk)
end

#10. Sieve of Eratosthenes

#http://zh.wikipedia.org/wiki/%E5%9F%83%E6%8B%89%E6%89%98%E6%96%AF%E7%89%B9%E5%B0%BC%E7%AD%9B%E6%B3%95                                                                             

n=120
primes = Array.new
for i in 0..n-2
 primes[i] = i+2
end   
index = 0 
while primes[index]**2 <= primes.last
      prime = primes[index]
      primes = primes.select { |x| x == prime || x%prime != 0 }
      index += 1
end
p primes