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/CAPAYYh7JR98QgXPyF43%3DRVABnaBviVcQB-aTO5kCsywribWzMw%40mail.gmail.com.
