text: #!/usr/bin/env python
  """Scientific Hello World script using a module hw."""
  import sys
  from hw import hw1, hw2
  
  try:
      r1 = float(sys.argv[1]);  r2 = float(sys.argv[2])
  except:
      print 'Usage:', sys.argv[0], 'r1 r2'; sys.exit(1)
  print 'hw1, result:', hw1(r1, r2)
  print 'hw2, result: ',
  hw2(r1, r2)
  
  # test hw3 (s as pointer):
  from hw import hw3
  s = hw3(r1, r2)
  print 'hw3, result:', s
  
  # test hw4 (s as reference):
  from hw import hw4
  s = hw4(r1, r2)
  print 'hw4, result:', s
  
  