On Wed, Jan 27, 2010 at 5:11 PM, Ronan Lamy <[email protected]> wrote: > Le mercredi 27 janvier 2010 à 16:52 -0800, Ondrej Certik a écrit : >> On Wed, Jan 27, 2010 at 4:39 PM, Ronan Lamy <[email protected]> wrote: >> > Le mercredi 27 janvier 2010 à 11:19 -0800, Ondrej Certik a écrit : >> >> What is the advantage of having two classes instead of one? Just so >> >> that I understand the motivation better. Essentially you just want to >> >> split Basic into two classes, so that each class is simpler to >> >> maintain? I am missing why it is a roadblock, but since you both did >> >> some work with assumptions already, I guess there is a good reason >> >> for that. >> > >> > The main problem is circular dependency: assuming we switch to the new >> > assumption system, algebraic expressions need assumptions, assumptions >> > need the logic module, and logic needs Basic. So if Basic is aware of >> > the existence of algebraic expressions, we have a problem. This also >> > means that Basic shouldn't be aware of assumptions, by the way. >> >> Basic should not be aware of assumptions at all, that's clear. >> >> So let's say I have x^2, which is Pow(Symbol("x"), 2). How does the >> Expr come into this? And why does it need to know about assumptions? I >> thought that's what refine() is for. > Expr is a base class of both Pow and Symbol, so its methods might be > called when working with x^2. It probably needs to know about some > assumptions (for instance whether x is commutative) in order to evaluate > some expressions (for instance (y*x^2)^2).
Besides commutative, does it need to know any other assumption? I think we might have a new NCMul for commutative multiplication. 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.
