In Sage 5.0rc0, I observe a weird phenomenon. See the following code
-----
from sage.rings.ring import CommutativeAlgebra
class NA(CommutativeAlgebra):
"""
"""
def __init__(self, i):
"""
"""
CommutativeAlgebra.__init__(self, i.base_ring())
self._ideal = i
-----
This has no problem
-----
sage: F.<a>=GF(16)
sage: P.<x,y,z>=F[]
sage: i = P.ideal([x,y,z])
sage: NA(i)
<class '__main__.NA_with_category'>
-----
But the following modified code results in an error. The difference is the
addition of the method "_repr_".
-----
from sage.rings.ring import CommutativeAlgebra
class NA(CommutativeAlgebra):
"""
"""
def __init__(self, i):
"""
"""
CommutativeAlgebra.__init__(self, i.base_ring())
self._ideal = i
def _repr_(self):
return "NA defined by %s." % self._ideal
-----
Here is the code that results in a traceback.
-----
sage: F.<a>=GF(16)
sage: P.<x,y,z>=F[]
sage: i = P.ideal([x,y,z])
sage: NA(i)
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
/Users/kwankyu/Workplace/sage/decoders/<ipython console> in <module>()
/Users/kwankyu/Workplace/sage/decoders/<string> in __init__(self, i)
/Users/kwankyu/Sage/sage-5.0.rc0/local/lib/python2.7/site-packages/sage/rings/ring.so
in sage.rings.ring.CommutativeAlgebra.__init__ (sage/rings/ring.c:13627)()
/Users/kwankyu/Sage/sage-5.0.rc0/local/lib/python2.7/site-packages/sage/rings/ring.so
in sage.rings.ring.CommutativeRing.__init__ (sage/rings/ring.c:9574)()
/Users/kwankyu/Sage/sage-5.0.rc0/local/lib/python2.7/site-packages/sage/rings/ring.so
in sage.rings.ring.Ring.__init__ (sage/rings/ring.c:1902)()
/Users/kwankyu/Sage/sage-5.0.rc0/local/lib/python2.7/site-packages/sage/structure/parent.so
in sage.structure.parent.Parent.__init__ (sage/structure/parent.c:4629)()
/Users/kwankyu/Sage/sage-5.0.rc0/local/lib/python2.7/site-packages/sage/categories/algebras.pyc
in __init_extra__(self)
138 mor = None
139 # This could be a morphism of
Algebras(self.base_ring()); however, e.g., QQ is not in Algebras(QQ)
--> 140 H = Hom(base_ring, self, Rings())
141
142 # Idea: There is a generic method "from_base_ring",
that just does multiplication with
/Users/kwankyu/Sage/sage-5.0.rc0/local/lib/python2.7/site-packages/sage/categories/homset.pyc
in Hom(X, Y, category)
157 global _cache
158 key = (X,Y,category)
--> 159 if _cache.has_key(key):
160 H = _cache[key]()
161 # What is this test for? Why does the cache ever contain a
0 value?
/Users/kwankyu/Sage/sage-5.0.rc0/local/lib/python2.7/site-packages/sage/structure/category_object.so
in sage.structure.category_object.CategoryObject.__hash__
(sage/structure/category_object.c:7329)()
/Users/kwankyu/Sage/sage-5.0.rc0/local/lib/python2.7/site-packages/sage/structure/sage_object.so
in sage.structure.sage_object.SageObject.__repr__
(sage/structure/sage_object.c:1496)()
/Users/kwankyu/Workplace/sage/decoders/<string> in _repr_(self)
/Users/kwankyu/Sage/sage-5.0.rc0/local/lib/python2.7/site-packages/sage/structure/parent.so
in sage.structure.parent.Parent.__getattr__ (sage/structure/parent.c:6732)()
/Users/kwankyu/Sage/sage-5.0.rc0/local/lib/python2.7/site-packages/sage/structure/parent.so
in sage.structure.parent.getattr_from_other_class
(sage/structure/parent.c:3248)()
AttributeError: 'NA_with_category' object has no attribute '_ideal'
sage:
-----
There is no such error in Sage 4.8
--
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