`uinv_as_power_series', `ureverse_inv_as_power_series'
------------------------------------------------------

uinv_as_power_series(P,D)
ureverse_inv_as_power_series(P,D)
     :: Computes the truncated inverse as a power series.

RETURN
     univariate polynomial

P
     univariate polynomial

D
     non-negative integer

   * For a polynomial P with a non zero constant term,
     `uinv_as_power_series(P,D)' computes a polynomial R whose degree
     is at most D such that P*R = 1 MOD x^(D+1), where X is the variable
     of P.

   * Let E be the degree of P.  `ureverse_inv_as_power_series(P,D)'
     computes `uinv_as_power_series(P1,D)' for P1=`ureverse(P,E)'.

   * The output of `ureverse_inv_as_power_series()' can be used as the
     input of `rembymul_precomp()'.

     [123] A=(x+1)^5;
     x^5+5*x^4+10*x^3+10*x^2+5*x+1
     [124] uinv_as_power_series(A,5);
     -126*x^5+70*x^4-35*x^3+15*x^2-5*x+1
     [126] A*R;
     -126*x^10-560*x^9-945*x^8-720*x^7-210*x^6+1
     [127] A=x^10+x^9;
     x^10+x^9
     [128] R=ureverse_inv_as_power_series(A,5);
     -x^5+x^4-x^3+x^2-x+1
     [129] ureverse(A)*R;
     -x^6+1

References
     *Note `utrunc udecomp ureverse': utrunc udecomp ureverse, *Note
     `udiv urem urembymul urembymul_precomp ugcd': udiv urem urembymul
     urembymul_precomp ugcd.

