Waldek, Thanks for the example of where the ordering of an OrderedVariableList is important in the library.
As I said, I will commit the code for comparable without this change. But I will be traveling for the next few days and may not be able to do the commit until some time next week. On Thu, Nov 12, 2009 at 11:00 PM, Waldek Hebisch <hebi...@math.uni.wroc.pl> wrote: > > Look at DistributedMultivariatePolynomial, note that order > is taken from DirectProduct(#vl,NonNegativeInteger). In > direct product we have lexicographic order in which > _lower numbered_ coordinate has more weight. Isn't this rather peculiar? Why does a lower numbered coordinate have more weight? > In lexicograhic order on monomials larger variable has > more weight. So order coming from representation agrees > with order from documentation only if you use current > definition of order for OrderedVariableList. I see. Thanks for finding this example. > You probably think that all algebra code is completely generic, > but this is not the case: lexicographic order is used because > it has very specific properties. Generic code means that > code makes only _necessary_ assumptions and properties > of monomial order are necessary for many computations. I have no problem to understand that properties of monomial order are necessary but I would prefer that it be specified explicitly by the organization of the code and not deeply hidden by unspecified assumptions. > Also, you may think that DistributedMultivariatePolynomial > should not make assumptions about representation > of OrderedVariableList. But representation is crucial > for efficiency and OrderedVariableList exist mainly to > support efficient polynomial computations with fixed > set of variables. > Yes I do think in general that DistributedMultivariatePolynomial (and other similar domains) should avoid making assumptions about representation where ever possible. I think that in most cases the representation can export methods that do not compromise performance significantly. In my opinion performance at the cost of maintainability is a questionable trade-off. Regards, Bill Page. -- You received this message because you are subscribed to the Google Groups "FriCAS - computer algebra system" group. To post to this group, send email to fricas-de...@googlegroups.com. To unsubscribe from this group, send email to fricas-devel+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/fricas-devel?hl=.
