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##############################################################################
#
# Copyright (c) 2003 Zope Foundation and Contributors.
# All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.1 (ZPL). A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE.
#
##############################################################################
"""Compute a resolution order for an object and its bases
"""
__docformat__ = 'restructuredtext'
def ro(object):
"""Compute a "resolution order" for an object
"""
return mergeOrderings([_flatten(object)])
def mergeOrderings(orderings, seen=None):
"""Merge multiple orderings so that within-ordering order is preserved
Orderings are constrained in such a way that if an object appears
in two or more orderings, then the suffix that begins with the
object must be in both orderings.
For example:
>>> _mergeOrderings([
... ['x', 'y', 'z'],
... ['q', 'z'],
... [1, 3, 5],
... ['z']
... ])
['x', 'y', 'q', 1, 3, 5, 'z']
"""
if seen is None:
seen = {}
result = []
orderings.reverse()
for ordering in orderings:
ordering = list(ordering)
ordering.reverse()
for o in ordering:
if o not in seen:
seen[o] = 1
result.append(o)
result.reverse()
return result
def _flatten(ob):
result = [ob]
i = 0
for ob in iter(result):
i += 1
# The recursive calls can be avoided by inserting the base classes
# into the dynamically growing list directly after the currently
# considered object; the iterator makes sure this will keep working
# in the future, since it cannot rely on the length of the list
# by definition.
result[i:i] = ob.__bases__
return result
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