Exercises in Programming Style

Chapter 11

Letterbox

11.1 Constraints

• The larger problem is decomposed into things that make sense for the problem domain.
• Each thing is a capsule of data that exposes one single procedure, namely the ability to receive and dispatch messages that are sent to it.
• Message dispatch can result in sending the message to another capsule.

11.2 A Program in this Style

  1 #!/usr/bin/env python
  2 import sys, re, operator, string
  3
  4 class DataStorageManager():
  5 """ Models the contents of the file """
  6 _data = ''
  7
  8 def dispatch(self, message):
  9  if message[0] == 'init':
 10    return self._init(message[1])
 11  elif message[0] == 'words':
 12    return self._words() ...