On Jul 4, 2008, at 10:44 AM, John H Palmieri wrote: >> >>> So I'm very confused. Any ideas what I should look at to try to fix >>> this? >> >> Yes, Sage caches some information so it doesn't have to do the logic >> anew on each arithmetic operation. One thing to check is if A5 == A7 >> succeeds. If you could post the traceback I could see if anything >> stands out to me. > > Here's an example. > > sage: A5 = SteenrodAlgebra(5); A7 = SteenrodAlgebra(7) > sage: A5 == A7 > False > sage: v = A5.P(2) > sage: w = A7.P(2,1) > sage: 2 * v > 2 P(2) > sage: 3 * w > ---------------------------------------------------------------------- > ----- > TypeError Traceback (most recent call > last) > > /Users/palmieri/<ipython console> in <module>() > > /Users/palmieri/element.pyx in > sage.structure.element.RingElement.__mul__ (sage/structure/element.c: > 8545)() > > /Users/palmieri/coerce.pyx in > sage.structure.coerce.CoercionModel_cache_maps.bin_op_c (sage/ > structure/coerce.c:5039)() > > /Users/palmieri/coerce.pyx in > sage.structure.coerce.CoercionModel_cache_maps.get_action_c (sage/ > structure/coerce.c:7864)() > > /Users/palmieri/coerce.pyx in > sage.structure.coerce.CoercionModel_cache_maps.discover_action_c > (sage/ > structure/coerce.c:8522)() > > /Users/palmieri/parent.pyx in > sage.structure.parent.Parent.get_action_c (sage/structure/parent.c: > 1843)() > > /Users/palmieri/parent.pyx in > sage.structure.parent.Parent.get_action_impl (sage/structure/parent.c: > 2005)() > > /Users/palmieri/parent.pyx in > sage.structure.parent.Parent.get_action_c_impl (sage/structure/ > parent.c:2672)() > > /Users/palmieri/parent.pyx in sage.structure.parent._register_pair > (sage/structure/parent.c:6360)() > > /Users/palmieri/parent.pyx in sage.structure.parent.EltPair.__eq__ > (sage/structure/parent.c:6183)() > > /Applications/sage/local/lib/python2.5/site-packages/sage/algebras/ > steenrod_algebra.py in __eq__(self, other) > 1528 Two elements are equal if their difference is zero. > 1529 """ > -> 1530 difference = self - other > 1531 return len(difference._raw['milnor']) == 0 > 1532 > > /Users/palmieri/element.pyx in > sage.structure.element.ModuleElement.__sub__ (sage/structure/ > element.c: > 5421)() > > /Users/palmieri/coerce.pyx in > sage.structure.coerce.CoercionModel_cache_maps.bin_op_c (sage/ > structure/coerce.c:5338)() > > TypeError: unsupported operand parent(s) for '-': 'mod 7 Steenrod > algebra' and 'mod 5 Steenrod algebra'
Ah, it looks like your __eq__ method is assuming that self and other are elements of the steenrod algebra. There are two solutions to this: 1) Use __cmp__ which (in Sage) will ensure that self and other have the same parent before it's called 2) Fix your __eq__ (and any other comparison methods you might have) to make sure self-other makes sense (or, as a quick fix, catch the type error here). - Robert --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-support URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
