Salut, Le code sur les espèces est connu pour être farci de bugs, et personne ne s'en est préoccupé depuis très longtemps. cf https://trac.sagemath.org/ticket/30727 Fred Le vendredi 11 décembre 2020 à 10:16:33 UTC+1, [email protected] a écrit :
> Dear all, > > I discovered a weird bug on power series when computing the inverse of a > serie. Look at this. > > This computation gives the expected result > > sage: L.<z> = LazyPowerSeriesRing(QQ) > > sage: f = 1 - z - z^2 > > sage: b = ~f > > sage: b.compute_coefficients(10) > > sage: b > > 1 + z + 2*z^2 + 3*z^3 + 5*z^4 + 8*z^5 + 13*z^6 + 21*z^7 + 34*z^8 + 55*z^9 > + 89*z^10 + O(x^11) > > But not this one: > > sage: L.<z> = LazyPowerSeriesRing(QQ) > > sage: f = 1 - z - z^2 > > sage: f.compute_coefficients(10) > > sage: f > > 1 - z - z^2 + O(x^11) > sage: b = ~f > > sage: b.compute_coefficients(10) > > sage: b > > 1 + z^1 + z^2 + z^3 + ... > > Another example with Catalan numbers > > sage: L.<z> = LazyPowerSeriesRing(QQ) > sage: C = L() > > sage: C.define(1 + z*C*C) > > sage: Cinv = ~C > > sage: Cinv.compute_coefficients(10); Cinv > > 1 - z - z^2 - 2*z^3 - 5*z^4 - 14*z^5 - 42*z^6 - 132*z^7 - 429*z^8 - > 1430*z^9 - 4862*z^10 + O(x^11) > > sage: C = L() > > sage: C.define(1 +z*C*C) > > sage: C.compute_coefficients(10);C > > 1 + z + 2*z^2 + 5*z^3 + 14*z^4 + 42*z^5 + 132*z^6 + 429*z^7 + 1430*z^8 + > 4862*z^9 + 16796*z^10 + O(x^11) > sage: Cinv = ~C > > sage: Cinv.compute_coefficients(10);Cinv > > 1 + z^1 + z^2 + z^3 + ... > > How Come?? > > This is Sage 9.2. I haven't tried on other versions > > -- 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 [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/sage-devel/f4ab89bb-0a1f-482f-a841-aa61e66507bcn%40googlegroups.com.
