Lecture Notes on 31 October 2012

def fib1 (n):
  if (n == 0) or (n == 1):
    return n
  else:
    return fib1 (n - 1) + fib1 (n - 2)

def fib2 (n):
  if (n == 0) or (n == 1):
    return n
  f0 = 0
  f1 = 1
  for i in range (1, n):
    f = f0 + f1
    f0 = f1
    f1 = f
  return f

def main():
  # test the fibonacci function
  print (fib1(8))
  print (fib2(8))

  # filter string
  s = "Hello World!"
  s = s.lower()
  p = ""
  for ch in s:
    if (ch.isalpha()):
      p = p + ch
  print (p)
main()