On May 18, 2:26 pm, Fabian Pedregosa <fab...@fseoane.net> wrote:
> Ondrej Certik wrote:
[...]
> > So here are some particular examples using sympy syntax:
>
> >>>> solve(Eq(x**2, 1), x)
> > [{x: 1}, {x: -1}]
>
> don't see the benefit over [1,-1]. It is clear that it is relative to x
> since you passed that argument to solve. Plus, it would make it harder
> to iterate over the solutions.
>
> In my oppinion it adds an unnecessary layer of complexity, but I'd love
> to see some examples where this results code shorted/more readable.I think it is only necessary for multidimensional equations involving several variables. > > > More tricky is if solve() can't do it, either because sympy can't do > > it, or because it's algebraically not possible. Mathematica returns an > > instance of a Solve() class (talking in sympy language) Like: > > >>>> solve(Eq(sin(x)+x, 0), x) > > Solve(Eq(sin(x)+x), x) > > Seems to me a good idea > > > and it also prints bunch of warnings (that can be suppressed), like: > > > Solve::tdep: The equations appear to involve the variables to be solved for > > in > > an essentially non-algebraic way. > > > But both me and Aaron like what Maple is doing: > > >>>> solve(Eq(sin(x)+x, 0), x) > > [RootOf(Eq(sin(x)+x), x, 1)] > > > At least sometimes you know the number of roots (one in the case > > above), so that's why the "1" above. I am not sure currently if even > > the number of roots is unknown. Then I think it should return: > > >>>> solve(Eq(sin(x)+x, 0), x) > > RootsOf(Eq(sin(x)+x), x) > > > which could behave like a dictionary. These RootOf and RootsOf classes > > can have some features, e.g. sometimes you know how to do some > > operation on the root (like squaring it), even without having an > > explicit formula for it. I really like RootOf(), it allows mixing algebraic and numerical solutions, like >>> solve((cos(x)+x)*x, x) [RootOf(cos(x)+x,x), 0] >>> _.evalf() [-0.7390851332151542, 0] It would be also more consistent with integrate() which returns an Integral() instead of raising a NotImplementedError. I'd be glad to have this in sympy! It would be much easier to fall back to numerical methods. Vinzent --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to sympy@googlegroups.com To unsubscribe from this group, send email to sympy+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sympy?hl=en -~----------~----~----~----~------~----~------~--~---
