niceSOFT/mpfr | Gitverse

src/sqrt_ui.c
54 строки2 KB
Vincent Lefèvre
03 янв 2018, 13:53
03 янв 2018, 13:532fce388
/* mpfr_sqrt_ui -- square root of a machine integer

Copyright 2000-2004, 2006-2018 Free Software Foundation, Inc.
Contributed by the AriC and Caramba projects, INRIA.

This file is part of the GNU MPFR Library.

The GNU MPFR 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 MPFR 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 MPFR Library; see the file COPYING.LESSER.  If not, see
http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */

#define MPFR_NEED_LONGLONG_H
#include "mpfr-impl.h"

int
mpfr_sqrt_ui (mpfr_ptr r, unsigned long u, mpfr_rnd_t rnd_mode)
{
  if (u)
    {
      mpfr_t uu;
      mp_limb_t up[1];
      int cnt;
      int inex;
      MPFR_SAVE_EXPO_DECL (expo);

      MPFR_TMP_INIT1 (up, uu, GMP_NUMB_BITS);
      MPFR_ASSERTN (u == (mp_limb_t) u);
      count_leading_zeros (cnt, (mp_limb_t) u);
      *up = (mp_limb_t) u << cnt;

      MPFR_SAVE_EXPO_MARK (expo);
      MPFR_SET_EXP (uu, GMP_NUMB_BITS - cnt);
      inex = mpfr_sqrt(r, uu, rnd_mode);
      MPFR_SAVE_EXPO_FREE (expo);
      return mpfr_check_range(r, inex, rnd_mode);
    }
  else /* sqrt(0) = 0 */
    {
      MPFR_SET_ZERO(r);
      MPFR_SET_POS(r);
      MPFR_RET(0);
    }
}