Exercises in Programming Style

Chapter 23

Declared Intentions

23.1 Constraints

• Existence of a type enforcer.
• Procedures and functions declare what types of arguments they expect.
• If callers send arguments of types that aren't expected, type errors are raised, and the procedures/functions are not executed.

23.2 A Program in this Style

  1 #!/usr/bin/env python
  2 import sys, re, operator, string, inspect
  3
  4 #
  5 # Decorator for enforcing types of arguments in method calls
  6 #
  7 class AcceptTypes():
  8 def __init__(self, *args):
  9  self._args = args
 10
 11 def __call__(self, f):
 12  def wrapped_f(*args):
 13    for i in range(len(self._args)):
 14    if type(args[i]) <> self._args[i]: ...