On Mon, Jan 26, 2009 at 2:34 PM, nico <[email protected]> wrote: > > >> I think that could be something like a global assumption. But it's >> true that I am still not convinced we need global assumptions. > > I agree with Vinzent about global assumptions.
Thanks for joining the discussion. > If x refers to a real in a whole session, I think it would be really > fastidious to use 'assume(x in R)' or something like that in every > calculation. That's right, but once we start to have anything global, it means that you can never be sure what happens if you write abs(x**2) anymore, becuase you simply don't know what global assumptions the user has. If, on the other hand, we don't have global assumptions, I don't think you need to use 'assume(x in R)' at every step. All you have to do is to refine the final answer, e.g. one command. Technically, I have nothing against global assumptions as long as they are made explicit, e.g. if you call e.refine() it would consult the global assumptions and refine the answer, but if you type abs(x**2), I think it can be quite dangerous --- but I know that a lot of other systems do that, so we might do that as well. In anycase, as a first step, we should implement local assumptions using refine() and when we get this working correctly, we may think if we want to do this globally and automagically. Ondrej --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/sympy?hl=en -~----------~----~----~----~------~----~------~--~---
