On Wed, Feb 10, 2021 at 7:05 PM gu...@uwosh.edu <gu...@uwosh.edu> wrote:
> I'm swamped with grading and class preparation, but wanted to comment > briefly on the items below: > > On Wednesday, February 10, 2021 at 3:58:21 PM UTC-6 asme...@gmail.com > wrote: > >> On Wed, Feb 10, 2021 at 1:44 PM Oscar Benjamin <oscar.j....@gmail.com> >> wrote: >> >> Yes, DivideSides would make sense for unevaluated division of >>> inequalities etc. >>> >>> That is not inconsistent with using + though: We can use eq1+eq2 as a >>> shorthand for the evaluated form of AddSides(eq1, eq2). For equations >>> that would always be able to evaluate. In Mathematica this is all >>> organised around making Boolean expressions that can evaluate after >>> substitution. >>> >> >> We can generalize this to applying any function to equations or >> inequalities. For equations, it matters where the function either isn't >> defined (like y=0 for f(x, y) = x/y), or isn't well-defined (for example, >> square roots are multivalued). For inequalities it matters on what parts of >> the domain the function is (strictly) monotonic. Except I don't know if >> SymPy can really answer either of these questions right now. So this might >> have to remain only a theoretical idea for the time being. >> >> Aaron Meurer >> >> >>> >>> Oscar >> >> I don't see a problem with returning multivalued/multiple equation > results. If I understand what you are talking about for expressions where > you have an equal sign this is working reasonably in the present > implementation. For example a simplified example of a quantum problem my > students just did: > [image: Screenshot from 2021-02-10 19-58-41.png] > The right hand size is of type `Piecewise`. > How would you handle dividing both sides of an equation by something? I don't know if a piecewise makes sense. (a = b)/x would be "a/x = b/x if x != 0, ??? otherwise". What meaningful thing could the ??? be? You can easily manipulate an equation into nonsense if you aren't careful about this (just Google "proof that 1 = 2"). But I don't know if SymPy should try to take responsibility to prevent it. Aaron Meurer > Jonathan > > -- > 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 view this discussion on the web visit > https://groups.google.com/d/msgid/sympy/a9cd201d-91b2-4bc1-b2fc-4cb0da3801b2n%40googlegroups.com > <https://groups.google.com/d/msgid/sympy/a9cd201d-91b2-4bc1-b2fc-4cb0da3801b2n%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 sympy+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/CAKgW%3D6%2BpAnDDP1V72J64Yz1Rrp3HPEEZoFtd_MPzQcm3Np_ezA%40mail.gmail.com.
