mpir/mpz/rootrem.c

/* mpz_rootrem(root, rem, u, nth) --  Set ROOT to floor(U^(1/nth)) and
   set REM to the remainder.

Copyright 1999, 2000, 2001, 2002, 2003, 2005 Free Software Foundation, Inc.

Copyright 2010 Dr B R Gladman

This file is part of the GNU MP Library.

The GNU MP Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 3 of the License, or (at your
option) any later version.

The GNU MP Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
License for more details.

You should have received a copy of the GNU Lesser General Public License
along with the GNU MP Library.  If not, see http://www.gnu.org/licenses/.  */

#include <stdio.h>		/* for NULL */
#include "gmp.h"
#include "gmp-impl.h"

void
mpz_rootrem (mpz_ptr root, mpz_ptr rem, mpz_srcptr u, unsigned long int nth)
{
  mp_ptr rootp, up, remp;
  mp_size_t us, un, rootn, remn;
  TMP_DECL;

  us = SIZ(u);

  /* even roots of negatives provoke an exception */
  if (us < 0 && (nth & 1) == 0)
    SQRT_OF_NEGATIVE;

  /* root extraction interpreted as c^(1/nth) means a zeroth root should
     provoke a divide by zero, do this even if c==0 */
  if (nth == 0)
    DIVIDE_BY_ZERO;

  if (us == 0)
    {
      if (root != NULL)
	SIZ(root) = 0;
      SIZ(rem) = 0;
      return;
    }

  un = ABS (us);
  rootn = (un - 1) / nth + 1;

  TMP_MARK;

  /* FIXME: Perhaps disallow root == NULL */
  if (root != NULL && u != root)
    rootp = MPZ_REALLOC (root, rootn);
  else
    rootp = TMP_ALLOC_LIMBS (rootn);

  if (u != rem)
    remp = MPZ_REALLOC (rem, un);
  else
    remp = TMP_ALLOC_LIMBS (un);

  up = PTR(u);

  if (nth == 1)
    {
      MPN_COPY (rootp, up, un);
      remn = 0;
    }
  else
    {
      remn = mpn_rootrem (rootp, remp, up, un, (mp_limb_t) nth);
    }

  if (root != NULL)
    {
      SIZ(root) = us >= 0 ? rootn : -rootn;
      if (u == root)
	MPN_COPY (up, rootp, rootn);
      else if (u == rem)
	MPN_COPY (up, remp, remn);
    }

  SIZ(rem) = us >= 0 ? remn : -remn;
  TMP_FREE;
}