On May 5, 2011, at 1:00 PM, Haz wrote: > > > On Thu, May 5, 2011 at 12:29 PM, Aaron Meurer <asmeu...@gmail.com> wrote: > > The big questions that remain are those involving (1): it is generally > > accepted that the old assumption system should give way to the new one, but > > to what extent we remove the old ones from the core? How the new ones > > replace the old ones? What is the syntax that we will use for them? What > > "assumptions" will we make about the assumption system? (i.e., local -vs- > > global context by default) > > Well, one of the biggest problems with having the assumptions in the > core is that any time you want to edit the assumptions you have to > edit the core. Having them separate should make them much more > extensible. > > It's worth picking apart that sentiment. When I say "to what extent we > remove the old ones from the core?", I am considering the fact that > is_positive may still remain as a function of Expr. The fact that it > internally calls an ask(...) of the new assumption system is besides the > point.
I mean that for example the logic to compute sqrt(x**2) => abs(x) or x is all in the core (that's just Pow(Pow(x, 2), S(1)/2)). If we want to add a new assumption that doesn't exist yet, we would have to modify all the core methods to handle it correctly. But if the core is just calling Ask() everywhere, or even better if simplification is left to some handle function like refine(), then this isn't a problem. Aaron Meurer > > Also, maybe I am wrong, but I think it would be easier to have > something like Ask(expr, Q.whatever, Assume(x>y)) with the new system. > At any rate, this sort of things cannot be done with our current > is_assumption system (how do you assume x>y using that?). > > These are a level of complex assumptions that are out of the scope of what > the new assumption system can handle. It requires a higher form of reasoning > (potentially FOL, etc). > > Cheers -- 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.
