This is definitely a bug, though I'm not sure as to the cause (I thought this used to work, but the register_* commands aren't as well developed or tested as the Parent-provided ones).
On Mon, Oct 14, 2013 at 9:49 AM, Nils Bruin <nbr...@sfu.ca> wrote: > On #14711 we ran into an existing difference with how coercions that are > "embeddings" are handled in coercion discovery: > > class pA(Parent): pass > class pB(Parent): pass > class pC(Parent): pass > > A=pA(); B=pB(); C=pC() > > BtoA=Hom(B,A)(lambda x: A(x)) > AtoC=Hom(A,C)(lambda x: C(x)) > A.register_coercion(BtoA) > A.register_embedding(AtoC) > > G=get_coercion_model() > G.discover_coercion(A,C) #finds AtoC > G.discover_coercion(B,A) #finds BtoA > G.discover_coercion(B,C) #does not find the composition of BtoA with AtoC > > If we use C.register_coercion(AtoC) instead, then all discoveries succeeds. > We are working on the assumption that the > coercion system is modeled by a directed graph on the parents and that a > coercion exists iff there is a path from the domain to the codomain. > It seems register_embedding isn't adding edges that are fully recognized. > > Is this intentional or is this a "bug" in the coercion system? In particular > Robert Bradshaw's opinion (as original author) would be very helpful. > > -- > You received this message because you are subscribed to the Google Groups > "sage-devel" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sage-devel+unsubscr...@googlegroups.com. > To post to this group, send email to sage-devel@googlegroups.com. > Visit this group at http://groups.google.com/group/sage-devel. > For more options, visit https://groups.google.com/groups/opt_out. -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at http://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/groups/opt_out.
