Dear Hsin-Po Wang, On 2018-01-30, Hsin-Po Wang <a.simple.peo...@gmail.com> wrote: > But it is still interesting to see if this is an unintentional bug in, say, > the coercion model and can be fixed.
We have sage: S4.has_coerce_map_from(S4.subgroups()[19]) True Hence, the coercion model is supposed to *automatically* convert the element S4.subgroups()[19][1] into an element of S4, and then do the multiplication. Oddly enough, sage: S4[1]*S4.subgroups()[19][1] (1,4,2,3) works (i.e., the right factor is automatically converted into the parent of the left factor), but sage: S4.subgroups()[19][1]*S4[1] doesn't work (as you reported). The coercion model chooses coercion to the left factor's parent, if there are coercions available in *both* directions. However, if there only is a coercion from the left factor's parent to the right factor's parent but not vice versa, that coercion is supposed to be used. So, shortly, it is a clear bug. I created https://trac.sagemath.org/ticket/24612 for it. Thank you for reporting it! Best regards, Simon -- 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 https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
