Hey all, (I'm cc'ing this to sage-devel, because I think there are people there who care about modular forms who might not read sage-support.)
So I've also posted a patch on #2674, which actually fixes both of these issues, as well as the fact that it currently is the case that adding an element of CuspForms(22) to an element of ModularForms(22) breaks. Now, I agree with William's point here: > Note that > > b[0] + 0 > > and > > 0 + b[0] > > should *not* work, since in each case that's a canonical coercion, > and there is no natural map from ZZ (the parent of 0) into CuspForms(...) > for any weight except 0. In Sage coercions should not happen automatically > unless they are in some way natural and well defined on the whole domain > of the coercion (in this case ZZ). > However, the modular forms code isn't the culprit -- it just tries to coerce in by calling the coercion code for the underlying free module. Here's why this actually works: sage: M = ZZ**3 sage: M(0) (0, 0, 0) sage: M(1) # goes boom > There are some canonical coercions that one *should* have in the context > of modular forms that aren't there, probably partly because this whole > "canonical > coercions" business was after I wrote the modular forms code. Here's > an example bug (=lack of a coercion that should be there): > > > sage: b=CuspForms(22).basis() > sage: sum(b, b[0].parent()(0)) This now works fine with the patch I posted to #2674. Currently, there are no coercions between different levels; which such coercions would people like to see? Coercing from Gamma0(M) to Gamma0(Md) seems plausible, though one argue that it's a choice of one specific degeneracy map. That is, it seems "standard" but not canonical. I think it's the same as asking for a natural map from ZZ['x'] to ZZ['y']. Of course, this works in Sage, so maybe the above map should, too. Maybe also maps from Gamma0 to Gamma1 and GammaH? And GammaH to Gamma1? Which maps seem reasonable to people? Jay, are there any of these that you would expect to work that don't? -cc --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-devel@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
