A new varaint for gtrunc on padics

[Michael Stoll <Michael_Stoll@math.uni-bonn.de>]

The following is a little bit cleaner (and more efficient in the
case that we have a p-adic unit). Patch is with respect to the
original pari-2.0.7.alpha source). (GN: Is this OK?)

Michael


lordly:/Users/micha/UnixProjects/pari/pari-2.0.7.alpha> diff -c2  
src/basemath/gen3.c.orig src/basemath/gen3.c
*** src/basemath/gen3.c.orig    Sun Apr 19 15:33:15 1998
--- src/basemath/gen3.c Mon Apr 20 19:47:33 1998
***************
*** 1699,1703 ****
  gtrunc(GEN x)
  {
!   long tx=typ(x),av,tetpil,i;
    GEN y;

--- 1699,1703 ----
  gtrunc(GEN x)
  {
!   long tx=typ(x),av,tetpil,i,v;
    GEN y;

***************
*** 1715,1720 ****
      case t_PADIC:
        if (!signe(x[4])) return gzero;
!       av=avma; y=gpuigs((GEN)x[2],valp(x)); tetpil=avma;
!       return gerepile(av,tetpil, mulii(y,(GEN)x[4]));

      case t_RFRAC: case t_RFRACN:
--- 1715,1733 ----
      case t_PADIC:
        if (!signe(x[4])) return gzero;
!       v=valp(x);
!       if (v==0) return (GEN)x[4]; /* simplest case */
!       if (v>0)
!       { /* here, p^v is an integer, so we can use mulii */
!         av=avma; y=gpuigs((GEN)x[2],v); tetpil=avma;
!         return gerepile(av,tetpil,mulii(y,(GEN)x[4]));
!       }
!       else
!       { /* result is the fraction x[4]/p^(-v);
!            should already be in lowest terms */
!         y=cgetg(3,t_FRAC);
!         y[1]=lcopy((GEN)x[4]);
!         y[2]=lpuigs((GEN)x[2],-v);
!         return y;
!       }

      case t_RFRAC: case t_RFRACN: