| # (C) Copyright David Abrahams 2001. Permission to copy, use, modify, sell and |
| # distribute this software is granted provided this copyright notice appears in |
| # all copies. This software is provided "as is" without express or implied |
| # warranty, and with no claim as to its suitability for any purpose. |
| |
| from utility import to_seq |
| |
| def difference (b, a): |
| """ Returns the elements of B that are not in A. |
| """ |
| result = [] |
| for element in b: |
| if not element in a: |
| result.append (element) |
| |
| return result |
| |
| def intersection (set1, set2): |
| """ Removes from set1 any items which don't appear in set2 and returns the result. |
| """ |
| result = [] |
| for v in set1: |
| if v in set2: |
| result.append (v) |
| return result |
| |
| def contains (small, large): |
| """ Returns true iff all elements of 'small' exist in 'large'. |
| """ |
| small = to_seq (small) |
| large = to_seq (large) |
| |
| for s in small: |
| if not s in large: |
| return False |
| return True |
| |
| def equal (a, b): |
| """ Returns True iff 'a' contains the same elements as 'b', irrespective of their order. |
| # TODO: Python 2.4 has a proper set class. |
| """ |
| return contains (a, b) and contains (b, a) |
