Karim BELABAS on Sat, 7 Sep 2002 23:04:01 +0200 (MEST) |
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Re: polcoeff |
On Sat, 27 Jul 2002, Ilya Zakharevich wrote: > It looks like polcoeff() is silently converting a rational function > into a power series. Is it a good thing to do? No. It is rather obcure, and quite useless since can have Ser() for explicit conversion. Since this was not documented, I call it a bug. I have removed that conversion, as I was fixing the polcoeff(1/x, -3) --> SEGV bug. > The fact that it *can* operates on power series *is* mentioned in the > docs, but not in the docs for the function. The fact that it would > coerce a "wrong" type is not mentioned at all... I have modified the docs: (22:04) gp > ??polcoeff polcoeff(x,s,{v}): coefficient of degree s of the polynomial x, with respect to the main variable if v is omitted, with respect to v otherwise. Also applies to power series, scalars (polynomial of degree 0), and to rational functions provided the denominator is a monomial. Karim. -- Karim Belabas Tel: (+33) (0)1 69 15 57 48 Dép. de Mathematiques, Bat. 425 Fax: (+33) (0)1 69 15 60 19 Université Paris-Sud Email: Karim.Belabas@math.u-psud.fr F-91405 Orsay (France) http://www.math.u-psud.fr/~belabas/ -- PARI/GP Home Page: http://www.parigp-home.de/