gnarmis

def maxPrimeFactor(n) #=> maxPrimeFactor(600851475143) => 6857 in 2007.562 ms
  # limit the ridiculous range safely
  range = n**(1/Math.sqrt(n.to_s.length).floor.to_f)
  ary = (1..range).to_a
  # Sieve of Eratosthenes (replace with Sieve of Atkin?)
  for i in ary
    for j in ary
      if i != j
        if (j % i == 0)
          ary.delete(j)

gnarmis

ruby-1.9.2-p180 :004 > def cat.has_nine_lives?
ruby-1.9.2-p180 :005?>   true
ruby-1.9.2-p180 :006?>   end
 => nil 
ruby-1.9.2-p180 :007 > cat.has_nine_lives?
 => true

gnarmis

ruby-1.9.2-p180 :001 > cat = Object.new
 => #<Object:0x0000010085bc58> 
ruby-1.9.2-p180 :002 > puts cat.methods.sort
!
!=
!~
<=>
==
===
=~