It's the difference between conversion and coercion. P = PolynomialRing(GF(2), "z", sparse=True); Q = PolynomialRing(ZZ, "z", sparse=False) sage: P.convert_map_from(Q) Conversion map: From: Univariate Polynomial Ring in z over Integer Ring To: Sparse Univariate Polynomial Ring in z over Finite Field of size 2 sage: P.convert_map_from(Q)(Q.gen()) z
David On Wed, Oct 12, 2022 at 5:15 PM 'Martin R' via sage-devel < sage-devel@googlegroups.com> wrote: > Sorry, I don't understand your last sentence. We have > > sage: P = PolynomialRing(GF(2), "z", sparse=True); Q = PolynomialRing(ZZ, > "z", sparse=False) > sage: P.has_coerce_map_from(Q) > False > > How does this fit with > > "And of course you can convert even when Q is not sparse."? > > Martin > > On Wednesday, 12 October 2022 at 23:04:38 UTC+2 David Roe wrote: > >> Yes, that's expected. >> >> sage: P = PolynomialRing(GF(2), "z", sparse=True); Q = PolynomialRing(ZZ, >> "z", sparse=True) >> sage: P.has_coerce_map_from(Q) >> True >> >> And of course you can convert even when Q is not sparse. >> David >> >> On Wed, Oct 12, 2022 at 4:58 PM 'Martin R' via sage-devel < >> sage-...@googlegroups.com> wrote: >> >>> I have no idea whether the following is to be expected: >>> >>> sage: P = PolynomialRing(GF(2), "z", sparse=False); Q = >>> PolynomialRing(ZZ, "z") >>> sage: P.has_coerce_map_from(Q) >>> True >>> >>> sage: P = PolynomialRing(GF(2), "z", sparse=True); Q = >>> PolynomialRing(ZZ, "z") >>> sage: P.has_coerce_map_from(Q) >>> False >>> >>> Martin >>> >>> -- >>> 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+...@googlegroups.com. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/sage-devel/c585103b-9dfa-4e25-b36b-20f8fb937435n%40googlegroups.com >>> <https://groups.google.com/d/msgid/sage-devel/c585103b-9dfa-4e25-b36b-20f8fb937435n%40googlegroups.com?utm_medium=email&utm_source=footer> >>> . >>> >> -- > 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 view this discussion on the web visit > https://groups.google.com/d/msgid/sage-devel/5d443b30-3171-4a6c-bfdc-c61100680cc9n%40googlegroups.com > <https://groups.google.com/d/msgid/sage-devel/5d443b30-3171-4a6c-bfdc-c61100680cc9n%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- 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 view this discussion on the web visit https://groups.google.com/d/msgid/sage-devel/CAChs6_m2adJrXP3%3Dhs%3D9AKCFcinFgGiOg_BHJ3%2BAOVVHPguERg%40mail.gmail.com.
