contrib/gmp/mpz/root.c

   1 /* mpz_root(root, u, nth) --  Set ROOT to floor(U^(1/nth)).
   2    Return an indication if the result is exact.
   3
   4 Copyright 1999, 2000, 2001, 2002, 2003, 2005 Free Software Foundation, Inc.
   5
   6 This file is part of the GNU MP Library.
   7
   8 The GNU MP Library is free software; you can redistribute it and/or modify
   9 it under the terms of the GNU Lesser General Public License as published by
  10 the Free Software Foundation; either version 3 of the License, or (at your
  11 option) any later version.
  12
  13 The GNU MP Library is distributed in the hope that it will be useful, but
  14 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  15 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
  16 License for more details.
  17
  18 You should have received a copy of the GNU Lesser General Public License
  19 along with the GNU MP Library.  If not, see http://www.gnu.org/licenses/.  */
  20
  21 #include <stdio.h>              /* for NULL */
  22 #include "gmp.h"
  23 #include "gmp-impl.h"
  24
  25 int
  26 mpz_root (mpz_ptr root, mpz_srcptr u, unsigned long int nth)
  27 {
  28   mp_ptr rootp, up;
  29   mp_size_t us, un, rootn, remn;
  30   TMP_DECL;
  31
  32   us = SIZ(u);
  33
  34   /* even roots of negatives provoke an exception */
  35   if (us < 0 && (nth & 1) == 0)
  36     SQRT_OF_NEGATIVE;
  37
  38   /* root extraction interpreted as c^(1/nth) means a zeroth root should
  39      provoke a divide by zero, do this even if c==0 */
  40   if (nth == 0)
  41     DIVIDE_BY_ZERO;
  42
  43   if (us == 0)
  44     {
  45       if (root != NULL)
  46         SIZ(root) = 0;
  47       return 1;                 /* exact result */
  48     }
  49
  50   un = ABS (us);
  51   rootn = (un - 1) / nth + 1;
  52
  53   TMP_MARK;
  54
  55   /* FIXME: Perhaps disallow root == NULL */
  56   if (root != NULL && u != root)
  57     rootp = MPZ_REALLOC (root, rootn);
  58   else
  59     rootp = TMP_ALLOC_LIMBS (rootn);
  60
  61   up = PTR(u);
  62
  63   if (nth == 1)
  64     {
  65       MPN_COPY (rootp, up, un);
  66       remn = 0;
  67     }
  68   else
  69     {
  70       remn = mpn_rootrem (rootp, NULL, up, un, (mp_limb_t) nth);
  71     }
  72
  73   if (root != NULL)
  74     {
  75       SIZ(root) = us >= 0 ? rootn : -rootn;
  76       if (u == root)
  77         MPN_COPY (up, rootp, rootn);
  78     }
  79
  80   TMP_FREE;
  81   return remn == 0;
  82 }