In physics.mechanics, I actually tried to side-step this entire problem, by just using .x, .y, and .z for the three directions. We also allowed for users to define a custom string for an index, and access that direction via a dictionary using the index they defined (['1'], ['2'], ['3'], or ['i'], ['j'], ['k'], etc). But yeah, as Aaron said, we only had three dimensions. I don't know if that solution will be of any use to you.
-Gilbert On Fri, Nov 22, 2013 at 2:48 PM, Aaron Meurer <[email protected]> wrote: > I personally think that 0 or 1, the most important thing is to be > consistent. Because the worst is switching between the two. So, since > the rest of Python and SymPy uses 0-based, I would use that. And > anyway, you will ultimately store things in a Python list, so it would > be awkward to always switch from 1-based indexing on the user side and > 0-based on the internal side. > > With that being said, I seem to remember that the mechanics module > uses 1-based indexing for its representation of three dimensions. I > think it gets away with it because it only cares about those three > dimensions, so it can just use named variables like x1, x2, x3 instead > of x[0], x[1], x[2] (someone correct me if I am wrong). > > Aaron Meurer > > On Fri, Nov 22, 2013 at 2:53 PM, Ondřej Čertík <[email protected]> > wrote: > > On Fri, Nov 22, 2013 at 2:33 PM, F. B. <[email protected]> wrote: > >> Hi, I was recently facing a problem in Newtonian mechanics vs. special > >> relativity: textbooks represent Newtonian objects as 1-offset > >> vector/matrices/tensors, while in special relativity they are 0-offset > ones, > >> by the addition of a time-like dimension. > >> > >> I was drafting on my IPython notebook some ways to make classical > mechanics > >> work along with special relativity, and this problem seems to be an > issue, > >> unless it simply gets ignored by breaking compatibility with textbooks > and > >> by shifting indices when passing from classical to relativistic > mechanics. > >> > >> Do you think that an offset on index-counting for > vectors/matrices/tensors > >> could be a good idea? > > > > For sure we should allow indexing from 1 or from 0, depending on the > physical > > and mathematical context. > > > > This is related to this: > > > > > https://plus.google.com/u/0/+Ond%C5%99ej%C4%8Cert%C3%ADk/posts/8FKW6vyuKsy > > > > and your example of i=1, 2, 3 (classical mechanics) vs mu=0, 1, 2, 3 > > (special/general relativity/QFT) > > is a great one. > > > > Ondrej > > > > P.S. I've seen also the mu=1, 2, 3, 4 usage in some older textbooks, > > where 1, 2, 3 is the same as in classical mechanics and 4th is the > > time. But I would not encourage this usage and rather follow the usual > > modern physics notation. > > > > -- > > 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 post to this group, send email to [email protected]. > > Visit this group at http://groups.google.com/group/sympy. > > 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 [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/sympy. > 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 [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sympy. For more options, visit https://groups.google.com/groups/opt_out.
