Thanks for sharing this. Just one comment. I wouldn't let the mechanics way prevent you all from doing this the "right" way. With the right way being whatever a more general approach is. The mechanics module was designed from a very narrow point of view in terms of the mathematics. Without thinking about this very hard, it seems that whatever we do in mechanics has got to be some small subset of the generalities of vector calculus but we make sure to really carefully deal with the details that most affect our systems (rotations, vectors, reference frames, time differentiation).
I'm looking forward to seeing some of the problems done out by hand that are outside the scope of the way we think about this from the mechanics perspective. Maybe then I can comment better on the how mechanics would work with a generalization. The stress test you wrote out is a nice start. Jason moorepants.info +01 530-601-9791 On Tue, Jun 4, 2013 at 3:57 PM, Stefan Krastanov <krastanov.ste...@gmail.com > wrote: > And to be mean I will also write this down using the diffgeom module :) > > Seriously though, while the diffgeom module uses a completely different > approach that is not compatible with the needs of the `mechanics` module > (on which we are focusing), having such a comparison will be useful to show > bad choices both in the diffgeom module and in the present project. > > > On 5 June 2013 00:46, Stefan Krastanov <krastanov.ste...@gmail.com> wrote: > >> Here is a quick summary from today: >> >> - probably scalar fields will be represented simply by SymPy expressions >> where some of the symbols will have special meaning (the coordinates) >> - probably vectors will be represented like in mechanics (one object, not >> necessarily a sympy expression) >> >> - using reference systems translated and rotated with respect to each >> other is rather unclear at the moment: before continuing with the irc >> meetings I would suggest that the students provide a _nice_ wiki presenting >> the answers to the questions in the previous thread and also the following >> questions: >> >> Bellow is the question in "mathematical" terms. Transform it in whatever >> way you find appropriate to fit your suggested APIs: >> >> - in 3D >> - I have three points A, B and C. >> - I use each of them as the zero of three different coordinate systems >> - The A and B systems are both Cartesian but rotated by theta_AB around >> axis_AB >> - The C system is spherical (r, phi, theta). The theta=0 axis is rotated >> wrt the z axis of A by the Euler angles alpha, beta, gamma >> - I define a scalar field in A, another scalar field in B and a vector >> field in C >> - I want the sum of the scalar fields >> - I want the gradient of that sum >> - I want the convective derivative of the vector field from C wrt the >> gradient from the question above >> - I want to express the entities from the above 4 question in each of the >> three coordinate systems. >> - For all this please explicitly choose some fields for the examples and >> calculate the expected results by hand (and add them to the example session >> as mock results). >> >> I think that this will really stress test the suggested API. The only >> thing missing is the time dependence needed in mechanics. I strongly >> suggest that we first finish the considerations above before continuing. >> >> @Prasoon and Sachin, when will you be able to provide a detailed wiki >> page with an example session for what is asked here? There is really no >> need to hurry (officially GSoC has not started yet) so please take your >> time (a week?). >> >> Stefan >> >> >> On 4 June 2013 01:12, Aaron Meurer <asmeu...@gmail.com> wrote: >> >>> The discussion was at http://piratepad.net/KBviCWUlA3. >>> >>> I'm curious what you think of this kind of discussion, as opposed to >>> IRC. Google docs is also an option (it has a chat). I think the >>> downside is that unlike IRC, which is logged at >>> http://colabti.org/irclogger/irclogger_logs/sympy, it's a little >>> harder to search through these discussions afterwords. >>> >>> Aaron Meurer >>> >>> >>> On Mon, Jun 3, 2013 at 4:16 PM, Stefan Krastanov >>> <krastanov.ste...@gmail.com> wrote: >>> > Today we had the first discussion with Prasoon and Sachin about their >>> > projects. >>> > >>> > We did not progress much but at least we outlined the two general >>> approaches >>> > that we can use for these modules (specifically for creating vector >>> fields). >>> > I will give them somewhat arbitrary names here: >>> > >>> > - the `mechanics` way - having a Vector class that keeps all the >>> information >>> > about the field and it is not part of expression trees in the way >>> Basic and >>> > Expr are. For instance Vector(something along >>> cartesian.x)+Vector(something >>> > along spherical.r) will result in Vector(complex internal structure). >>> > >>> > - the `diffgeom` way - having base/unit vectors and building all the >>> rest in >>> > terms of their linear combinations (all this expressed as sympy >>> > expressions). >>> > >>> > >>> > >>> > Prasoon and Sachin did not have the time to look at the example >>> problem that >>> > was given in the previous email yet (no harm done there, there is >>> still some >>> > time before the official starting date). Probably this will be the >>> subject >>> > of our next discussion. >>> > >>> > The next discussion was scheduled for tomorrow. After that I suggest >>> that we >>> > keep most of the discussions to the mailing list and the gihub wiki >>> and meet >>> > on irc / realtime wikis / google docs / etc once a week. >>> > >>> > Stefan >>> > >>> > -- >>> > You received this message because you are subscribed to the Google >>> Groups >>> > "sympy" group. >>> > To unsubscribe from this group and stop receiving emails from it, send >>> an >>> > email to sympy+unsubscr...@googlegroups.com. >>> > To post to this group, send email to sympy@googlegroups.com. >>> > Visit this group at http://groups.google.com/group/sympy?hl=en-US. >>> > For more options, visit https://groups.google.com/groups/opt_out. >>> > >>> > >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "sympy" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to sympy+unsubscr...@googlegroups.com. >>> To post to this group, send email to sympy@googlegroups.com. >>> Visit this group at http://groups.google.com/group/sympy?hl=en-US. >>> For more options, visit https://groups.google.com/groups/opt_out. >>> >>> >>> >> > -- > You received this message because you are subscribed to the Google Groups > "sympy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sympy+unsubscr...@googlegroups.com. > To post to this group, send email to sympy@googlegroups.com. > Visit this group at http://groups.google.com/group/sympy?hl=en-US. > For more options, visit https://groups.google.com/groups/opt_out. > > > -- You received this message because you are subscribed to the Google Groups "sympy" group. 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