Some ways to handle a fibonacci sequence in Ruby

Fib.rb

# This prints out the nth member of the sequence
def fib(n)
  last_two = [0,1]
  3.upto(n) do
    last_two = last_two[1], last_two.inject(:+)
  end

  puts last_two.last
end

# This prints out the first 20 members
(1..20).inject( [0, 1] ) { | fib | fib << fib.last(2).inject(:+) }