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).
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