fibenum.rb

require 'enumerator'
class FibonacciSeq
  include Enumerable
  def initialize
    @prev = 0
    @curr = 1
  end

  def each(&block)
    if block_given?
      loop do
        @prev, @curr = @curr, @prev + @curr
        block.call(@prev)
      end
    else
      Enumerator.new(self)
    end
  end
end

p FibonacciSeq.new.first

p FibonacciSeq.new.first(10)

enum = FibonacciSeq.new.each
1.upto(10) do |i|
  p enum.next
end

results.txt

$ rvm 1.8.7,1.9.2,jruby,jruby-head do ruby -v r.rb
ruby 1.8.7 (2011-06-30 patchlevel 352) [i686-darwin11.0.1]
1
[1, 1, 2, 3, 5, 8, 13, 21, 34, 55]
/Users/nicksieger/.rvm/rubies/ruby-1.8.7-p352/lib/ruby/1.8/generator.rb:188: warning: method redefined; discarding old next
/Users/nicksieger/.rvm/rubies/ruby-1.8.7-p352/lib/ruby/1.8/generator.rb:200: warning: method redefined; discarding old rewind
1
1
2
3
5
8
13
21
34
55
ruby 1.9.2p290 (2011-07-09 revision 32553) [x86_64-darwin11.0.1]
1
[1, 1, 2, 3, 5, 8, 13, 21, 34, 55]
1
1
2
3
5
8
13
21
34
55
jruby 1.6.5 (ruby-1.8.7-p330) (2011-10-25 9dcd388) (Java HotSpot(TM) Client VM 1.6.0_29) [darwin-i386-java]
1
[1, 1, 2, 3, 5, 8, 13, 21, 34, 55]
1
1
2
3
5
8
13
21
34
55
jruby 1.7.0.dev (ruby-1.8.7-p357) (2012-01-12 0e83d96) (Java HotSpot(TM) Client VM 1.6.0_29) [darwin-i386-java]
[1]
[[1], [1], [2], [3], [5], [8], [13], [21], [34], [55]]
1
1
2
3
5
8
13
21
34
55