i discovered a bug when i tried to use a Set as a dictionary key. i've
included a patch below. i have also created a test case illustrating the
bug -- in the future, where do i put this in the code/docs so it can go in
the patch too?
here is the test case:
---
In [72]: d={Set([2*I,1+I]):1}
In [73]: d[Set([1+I,2*I])]
<type 'exceptions.KeyError'>
---
note that this bug only occurs when python doesn't know
how to sort the elements in the Set. e.g.:
In [74]: d={Set([1,2]):1}
In [75]: d[Set([2,1])]
Out[75]: 1
works because Set([1,2]) and Set([2,1]) print the same:
In [76]: Set([1,2])
Out[76]: {1, 2}
In [77]: Set([2,1])
Out[77]: {1, 2}
while
In [78]: Set([2*I,1+I])
Out[78]: {2.00000000000000*I, 1.00000000000000 + 1.00000000000000*I}
In [79]: Set([1+I,2*I])
Out[79]: {1.00000000000000 + 1.00000000000000*I, 2.00000000000000*I}
print differently.
this in turn led to a different hash value, since the default hash value
comes from the string representation.
---
below is the patch.
# HG changeset patch
# User Kyle Schalm <[EMAIL PROTECTED]>>
# Date 1176451637 18000
# Node ID bca0cc86fd5e88dc21887c5d222c1fcfa71ae490
# Parent 76e21a785e866569cc43a15b01ee81d9dd131b43
fix bug when using Set as dictionary key
diff -r 76e21a785e86 -r bca0cc86fd5e sage/sets/set.py
--- a/sage/sets/set.py Fri Apr 13 00:29:21 2007 -0500
+++ b/sage/sets/set.py Fri Apr 13 03:07:17 2007 -0500
@@ -505,7 +505,7 @@ class Set_object_enumerated(Set_object):
def _repr_(self):
s = str(self.set())
- return "{" + s[5:-2] + "}"
+ return "{" + s[11:-2] + "}"
# return "Finite set of elements of %s"%self.__object
def set(self):
@@ -530,8 +530,11 @@ class Set_object_enumerated(Set_object):
try:
return self.__set
except AttributeError:
- self.__set = set(self.object())
+ self.__set = frozenset(self.object())
return self.__set
+
+ def __hash__(self):
+ return hash(self.set())
def __cmp__(self, other):
"""
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