Re: transforming a monic polynomial

[Karim BELABAS <Karim.Belabas@math.u-psud.fr>]

[Igor:]
> Hi, is there a command in gp to quickly convert a non-monic polynomial
> into a monic one?  nfinit(pol,2).pol would do, but it becomes
> senseless when poldisc is big and hard to factor.  I thought
> poltschirnhaus(pol) would work, but it doesn't always return monic
> polynomials.  

There isn't. Use the following (e.g. read from .gprc) :

pol_to_monic(x) =     \\  if version < 2.0.13, replace with
{ local(a,v);         \\  { pol_to_monic(x, /* locals: */ a,v) = 
  a = pollead(x);
  v = variable(x);
  subst(x,v,v/a) * a^(poldegree(x) - 1);
}

   Karim.
--
Karim Belabas                    email: Karim.Belabas@math.u-psud.fr
Dep. de Mathematiques, Bat. 425
Universite Paris-Sud             Tel: (00 33) 1 69 15 57 48
F-91405 Orsay (France)           Fax: (00 33) 1 69 15 60 19
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