On Wednesday, January 4, 2017 at 7:54:57 AM UTC-6, Marc Mezzarobba wrote: > > Daniel Krenn wrote: > > In the doc of sage.rings.qqbar.AlgebraicRealField._coerce_map_from_ > > there is the following test: > > > > sage: K.<a> = QuadraticField(7, embedding=AA(7).sqrt()) > > sage: AA.has_coerce_map_from(K) > > True > > > > Why does this return (correctly) True, although the code of this > > method is simply > > > > def _coerce_map_from_(self, from_par): > > return (from_par is ZZ or from_par is QQ > > or from_par is AA) > > > > ? > > Probably because NumberField_generic.__init__() does: > > self._populate_coercion_lists_(embedding=embedding) >
That is not true. Note that Foo.has_coerce_map_from() is not Foo._coerce_map_from_(). The method has_coerce_map_from() calls _coerce_map_from_, which should either return a coercion map or True, and in the latter case, then it uses Foo(bar) to define the coercion (which really uses _element_constructor_). What has_coerce_map_from() does is it checks to see if _coerce_map_from_() returns something that is not False (or perhaps None, I forget off-hand). Best. Travis -- 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.
