On 10/6/2010 2:58 PM, kj wrote:
These objects are non-mutable once they are created,
See below.
like to use a two-step comparison for equality, based on the
assumption that I can compute (either at creation time, or as needed
and memoized) a hashkey/digest for each object. The test for
equality of two of these objects would first compare their hashkeys.
If they are different, the two objects are declared different; if
they match, then a more stringent test for equality is performed.
I believe Python strings do this (cache the hash). Equality comparison
can check length, hashes, and only then chars.
So the problem is to come up with a reasonable hashkey for each of
these objects. The objects have two significant attributes, and
two of these objects should be regarded as equal if these attributes
are "the same" in both. The first attribute is a simple dictionary
whose keys are integers and values are strings. The second attribute
is more complicated. It is a tree structure, represented as a
dictionary of dictionaries of dictionaries... until we get to the
leaf elements, which are frozensets of strings. The keys at every
level of this structure are strings. E.g. a simple example of such
an attribute would look like:
{'A': {'a': set(['1', '2', '3']),
'b': set(['4', '5'])},
'B': set(['6', '7', '8'])}
If these two attributes, and hence the dicts, are public, then your
instances are mutable.
--
Terry Jan Reedy
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