> @Stefan. I agree about the tree traversals part. However, I still feel there > must be a way for the user to check if two scalar fields expressed in > different ways are mathematically equivalent. Could you suggest a way? Maybe > just another function?
This is described in one of the first pages of the sympy documentation: Checking for equality in general is mathematically impossible. In practice most of the time one does `simplify(expr_a - expr_b)` and sees whether he gets 0. In numerics one just plots the difference. > Also, have a look at the __eq__ function of the current Vector class. The current Vector class is not really a part of SymPy. One of the reasons that these two projects are useful is that they will make mechanics and sympy more inter-operable so stuff like `simplify` can be used seamlessly in mechanics. > I would really like atleast _some_ way of checking mathematical equality. As I mentioned above, there is already a way for that and the issues surrounding it are described in the docs (well, the documentation can be better, that is clear :) Anyway, given all these issues I can not imagine an api similar to the currently suggested one working well with sympy. Both ScalarField and Vector will break most of sympy if they eagerly eat all expressions that are added to them. Unrelated to that, ScalarField is ill defined because all the confusion around reference frames and coordinate systems and reuse of Symbols. Reference Frames and/or Coordinate Systems are represented as mutable objects which is nonsensical mathematically (one does not change how to references relate (one might want to parametrize something wrt time, but this is not the same))... @Sachin and Prasoon, can you work together on the next iteration of the design that is meant to fix these issues? When would you be able to show it? Multiple times I have suggested partial/fragmented designs similar to `diffgeom`. While some parts of `diffgeom` have no place here, some of the ideas (the representation of general fields based on sympy expressions containing base fields) could be helpful in preserving all the invariants important for sympy. Do you want me to provide a more complete suggestion on which you can base yours, or do you prefer to continue on your own for the moment? -- 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.
