# Arrays
x = Array.new()
x.push(5)
x.push(Array.new())
x.push(7)
x.pop() #returns 7
y = x
y.pop() #returns []
x.pop() #returns 5 -- x and y are aliased
x.push(6).push(7)
y = x.clone()
y.pop() # returns 7
x.pop() # returns 7 also
x = Array.new(3) # returns [nil, nil, nil]
x = [5, 6, 7]
x = Array.new(3) {|n| n + 5}
x = Array.new(3, 6) # returns [6, 6, 6]
puts x[1] #6
x[1] = 666
puts x[1] #666
puts x[20] #nil
puts x[-2] #666
x.delete(6) # deletes all values 6 from the array
x # is now []


# Hashes
x = Hash.new()
x["a"] = "Found A"
x[false] = "Found false"
puts x["a"]
puts x[false]
puts x.keys
puts x.values

x = Hash.new("NOT FOUND")
x["a"] = "Found A"
x["b"] = "Found B too"
puts x["a"]
puts x["c"]
x.delete("a") # returns "Found A" and deletes it from the hash

# Class variables and methods
class Foo
  @@counter = 0 # must initialize
  def initialize
    @@counter++
  end
  def Foo.report1
    @@counter
  end
  def self.report2 # same thing as Foo.report1
    @@counter
  end
end
x = Foo.new
y = Foo.new
numFoos = Foo.report1 # returns 2 -- note it doesn't require a Foo object to run