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