Hi there, I'm working on #11576 "make it possible to generate sequences of variables easily". I actually need to achieve a larger goal: I need to have symbolic variables indexed by any Sage objects (eg: integers, group element, matrices...). As as said previously here, I started to work on Burcin patch. So I extended a little Burcin patch. Now I'm faced with the problem that GiNaC indexed variable seems to have a not trivial semantic that I don't understand at all. Moreover I don't know how to debug Cython / C++ code so I'm quite stuck. Here is the problem I have:
To get it you should apply attachment:indexed_expression-experimental-fh.patch from #11576 on a fresh Sage-4.7.2 install. Then I can sage: m1 = matrix([1,2]); m1.set_immutable() sage: m2 = matrix([2,1]); m2.set_immutable() sage: a = x.ind[m1]; b = 2*x.ind[m2] sage: a + a 2*x.[1 2] sage: a + b x.[1 2] + 2*x.[2 1] which is, in my view very cool ! However strange thing has occurred under the hood, in particular for a strange reason I don't understand Sage added the two matrices ! This is apparent in sage: a = x.ind[Permutation([3,2,1])]; b = 2*x.ind[1] sage: a+b --------------------------------------------------------------------------- TypeError Traceback (most recent call last) [...] TypeError: unsupported operand parent(s) for '-': '<class 'sage.combinat.permutation.Permutation_class'>' and 'Integer Ring' To make thing crystal clear (I hope): sage: class bla(SageObject): ... def __add__(self, other): ... print "Addition called" sage: a, b = x.ind[m1],2*x.ind[m2] sage: m1 = bla() sage: m2 = bla() sage: m1 + m2 Addition called sage: m1*m2 --------------------------------------------------------------------------- TypeError Traceback (most recent call last) /home/data/Sage-Install/sage-4.7.2/devel/sage-review/sage/symbolic/<ipython console> in <module>() TypeError: unsupported operand type(s) for *: 'bla' and 'bla' WTF ! Why is it adding or multiplying my indices for nothing ! It is a problem of Ginac ? of the wrapper ? or behind the chair and the screen ? Any help greatly appreciated ! Cheers, Florent -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
