Dear Jason, As to the speed of the new terms, I simply tried it, using the equations of motion of a one body pendulum. There is no difference to the older terms:
with the *body* version the the rhs has 863, 824 operations. with the axis version, 2 intermediate frames, the rhs has 43,722 operations. The operations count was *exactly* the same with older and newer terms. Take care, Peter On Mon 14. Feb 2022 at 18:04 Peter Stahlecker <[email protected]> wrote: > Dear Jason, > > Just read you latest addition about vectors and reference frames. > Small question: > In order to rotate a frame relative to another one, you use these terms > *A.orient_axis(N, ..)* > *A.orient_body_fixed(N, …)* > > I assume, these are the new versions for > A.orientnew(N, ‚Axis‘, …) > A.orientnew(N, ‚Body, …) > > You might recall, that I ‚empirically‘ found that the *Body* version > created much larger equations of motion compared to using ‚intermediate ‚ > *Axis*‘ versions. > > Is it better to use *orient_body_fixed,* to avoid this issue of larger > equations of motion? > > Thanks & take care! > Peter > > > > On Sun 6. Feb 2022 at 08:19 Peter Stahlecker <[email protected]> > wrote: > >> Dear Jason, >> >> Thanks a lot for your explanation! Clear! >> I checked on metaclasses, but I must admit I mostly understood, that a >> simple user like me should not mess with them! :-)) >> >> Peter >> >> On Sun 6. Feb 2022 at 07:49 Jason Moore <[email protected]> wrote: >> >>> Peter, >>> >>> All `dynamicsymbols` is, is: >>> >>> f = Function('f') >>> t = symbols('t') >>> f_of_t = f(t) >>> >>> The last line `f(t)` is generating a new class of type f, instead of >>> using a predefined class (look up metaclasses). So the user, typically not >>> aware of this element in Python, is confused about what they are working >>> with in the last line. It is just the way SymPy Function works. There are >>> open issues about trying to change it to something more sensible for the >>> user to understand. >>> >>> Jason >>> moorepants.info >>> +01 530-601-9791 >>> >>> >>> On Sun, Feb 6, 2022 at 7:39 AM Peter Stahlecker < >>> [email protected]> wrote: >>> >>>> My question is more for my ‚general education‘ in sympy. >>>> >>>> I write this little program >>>> >>>> *from sympy.physics.mechanics import ** >>>> *import sympy as sm* >>>> *a = dynamicsymbols(‚a‘)* >>>> *b = sm.symbols(‚b‘)* >>>> >>>> *print(‚type of a:‘, type(a))* >>>> *print(‚type of b:‘, type(b))* >>>> >>>> I get this result: >>>> >>>> *type of a: a* >>>> *type of b: class sympy.core.symbols.Symbols* >>>> >>>> Is seems that *a* does not have a type. How can that be? I thought in >>>> python ‚everything‘ has a type. >>>> >>>> Thanks! >>>> Any explanation is highly appreciated! >>>> >>>> >>>> >>>> >>>> -- >>>> 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 [email protected]. >>>> To view this discussion on the web visit >>>> https://groups.google.com/d/msgid/sympy/5db2836e-44a8-428f-8b82-c56b2b2b5b20n%40googlegroups.com >>>> <https://groups.google.com/d/msgid/sympy/5db2836e-44a8-428f-8b82-c56b2b2b5b20n%40googlegroups.com?utm_medium=email&utm_source=footer> >>>> . >>>> >>> -- >>> 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 [email protected]. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/sympy/CAP7f1Ajkjs%3DNhJOhrFXmEpLJ6nv0TM9FgHXg%3DS1kSCF-6Cw5zw%40mail.gmail.com >>> <https://groups.google.com/d/msgid/sympy/CAP7f1Ajkjs%3DNhJOhrFXmEpLJ6nv0TM9FgHXg%3DS1kSCF-6Cw5zw%40mail.gmail.com?utm_medium=email&utm_source=footer> >>> . >>> >> -- >> Best regards, >> >> Peter Stahlecker >> > -- > Best regards, > > Peter Stahlecker > -- Best regards, Peter Stahlecker -- 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 [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/CABKqA0YLxUq3drDz4Zz5rM_bsE9nhLtf8onVhG_86eXxrAhL0w%40mail.gmail.com.
