On Tue, May 27, 2008 at 3:56 PM, Friedrich Hagedorn <[EMAIL PROTECTED]> wrote: > > On Tue, May 27, 2008 at 05:22:54AM -0700, astozzia wrote: >> >> evec=dvecM/sqrt(s.dot(dvec,dvec)) >> >> Note that I had to use the 'Matrix' and divide my the norm of the >> 'list'. Kinda weird... > > The problem is that we dont have a true vector support in sympy yet. > Specialy you cant define a function of a matrix/vector, thats bad. > > The derivation of > > In [4]: vec = s.array([cos(phi(t)),x(t),z(t)]) > In [5]: dvec = diff(vec,t) > > is simply done by a 'elementwise' derivation of the single elements > of the vec array. From the mathematical point of view I think this > isnt ideal. The 'diff(vec, t)' should better wrapped to something > like the jacobion matrix. > > We had a long discussion an sympy-patches > > > http://groups.google.com/group/sympy-patches/browse_thread/thread/78bf61123b3d7405 > > where I had sum up my opinion. But you know the time is raw ... :-)
I think simply one has to write a patch for that and if it's good it will go in. > And I am not sure if its so good to do this (vector extension) in sympy > because I think the sympycore project had a better > (mathematical) structure for that. Unfortunately, sympycore is a different project not directly usable by sympy (we may include it in thirdparty, but that's still not the solution imho, but at least we can then easily use one or the other, before someone will merge things completely, which unfortunately, will take much longer). However, I have always been all for merging our efforts. Could you please summarize which structure in sympycore is better? Let's use the same way in sympy. I read that discussion in sympy-patches ---- I am not sure what exactly you propose, and which things you agreed with Basti and which not. So let's get things moving. Basically, a good measure how to determine if something is useful/worthy is just to write a patch, try if all tests pass and if they do, and the patch is maintainable, it will go in. You don't have to write a real patch, just think about things in this way. So for example the vectorize patch is in, because it's basically just one or two lines of code (that applies the vectorization) and we may easily change it or even remove it if we ever have to. If you (or someone else) writes something better, sure it will go in. Ondrej --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sympy?hl=en -~----------~----~----~----~------~----~------~--~---
