wiki_fsm.rb

def step(state, c)
  case state
  when :before
    if c == "\n"
      print "\n"
    else
      if c != ' '
        print c
        state = :inside
      end
    end
  when :inside
    case c
    when ' '
      state = :after
    when "\n"
      print "\n"
      state = :before
    else
      print c
    end
  when :after
    if c == "\n"
      print "\n"
      state = :before
    end
  end
end

loop do
  step(:before, STDIN.read(1))
end