On Saturday, July 5, 2014 5:10:26 AM UTC-7, F. B. wrote: > > > > On Friday, July 4, 2014 4:12:25 PM UTC, Matthew wrote: >> >> Only semi-related, but here is a small pattern matching project. It's >> strictly for non-associative operators and so not appropriate for SymPy. >> It does function decently though >> >> https://github.com/mrocklin/unification >> > > By the way, the associativity may be handled by flattening both the > expression and the pattern before starting the matching algorithm, and the > applying the conglomeration (that is, canonicalize both expression and > pattern). >
probably not unless both of the expressions are constant. how to order x+y against a+b if there are predicates associated with pattern variables... > > Mathematica has the attribute Flat to declare a node flat, so that the > flattening happens upon construction and all of the node's arguments are > considered associative wrt that node. The same for the attribute Orderless, > which considers all of the nodes to be commutative. > > I am wondering whether we should consider the associative property as > associated to the node/operator (as Mathematica does), or whether it should > be assigned to the tuple (operator, type of argument). I think that it's OK > to have a support for mixed commutativity of arguments (which Mathematica > does not natively support), but I think that associativity should be a > property of the node (it would become too garbled otherwise). > > Consider that the commutativity/non-commutativity can be further > generalized by associating a subgroup of the symmetric group to the node, > specifying more complex commutativity properties. SymPy already has support > for canonicalization of such cases, added by Pernici two years ago. > Unfortunately pattern matching would become even more garbled if this were > to be included. > -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sympy+unsubscr...@googlegroups.com. To post to this group, send email to sympy@googlegroups.com. Visit this group at http://groups.google.com/group/sympy. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/68d8b161-b501-41a8-8db2-290d4f9dbf46%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
