There would be a much simpler solution than allowing a new operator. Just allow the numpy function dot to take more than two arguments. Then A*B*C in matrix notation would simply be: dot(A,B,C)
with arrays. Wouldn't that make everybody happy? Plus it does not break backward compatibility. Am I missing something? == Olivier 2009/6/7 Tom K. <t...@kraussfamily.org> > > > Fernando Perez wrote: > > > > On Sat, Jun 6, 2009 at 11:03 AM, Charles R > > Harris<charlesr.har...@gmail.com> wrote: > > > >> I don't think we can change the current matrix class, to do so would > >> break > >> too much code. It would be nice to extend it with an explicit inner > >> product, > >> but I can't think of any simple notation for it that python would parse. > > > > Maybe it's time to make another push on python-dev for the pep-225 > > stuff for other operators? > > > > https://cirl.berkeley.edu/fperez/static/numpy-pep225/ > > > > Last year I got pretty much zero interest from python-dev on this, but > > they were very very busy with 3.0 on the horizon. Perhaps once they > > put 3.1 out would be a good time to champion this again. > > > > It's slightly independent of the matrix class debate, but perhaps > > having special operators for real matrix multiplication could ease > > some of the bottlenecks of this discussion. > > > > It would be great if someone could champion that discussion on > > python-dev though, I don't see myself finding the time for it another > > time around... > > > > How about pep 211? > http://www.python.org/dev/peps/pep-0211/ > > PEP 211 proposes a single new operator (@) that could be used for matrix > multiplication. > MATLAB has elementwise versions of multiply, exponentiation, and left and > right division using a preceding "." for the usual matrix versions (* ^ \ > /). > PEP 225 proposes "tilde" versions of + - * / % **. > > While PEP 225 would allow a matrix exponentiation and right divide, I think > these things are much less common than matrix multiply. Plus, I think > following through with the PEP 225 implementation would create a > frankenstein of a language that would be hard to read. > > So, I would argue for pushing for a single new operator that can then be > used to implement "dot" with a binary infix operator. We can resurrect PEP > 211 or start a new PEP or whatever, the main thing is to have a proposal > that makes sense. Actually, what do you all think of this: > @ --> matrix multiply > @@ --> matrix exponentiation > and we leave it at that - let's not get too greedy and try for matrix > inverse via @/ or something. > > For the nd array operator, I would propose taking the last dimension of the > left array and "collapsing" it with the first dimension of the right array, > so > shape (a0, ..., aL-1,k) @ (k, b0, ..., bM-1) --> (a0, ..., aL-1, b0, ..., > bM-1) > Does that make sense? > > With this proposal, matrices go away and all our lives are sane again. :-) > Long live the numpy ndarray! Thanks to the creators for all your hard work > BTW - I love this stuff! > > - Tom K. > -- > View this message in context: > http://www.nabble.com/matrix-default-to-column-vector--tp23652920p23907204.html > Sent from the Numpy-discussion mailing list archive at Nabble.com. > > _______________________________________________ > Numpy-discussion mailing list > Numpy-discussion@scipy.org > http://mail.scipy.org/mailman/listinfo/numpy-discussion >
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