| /* mpfr_sub_ui -- subtract a floating-point number and a machine integer |
| |
| Copyright 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc. |
| Contributed by the Arenaire and Cacao 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 2.1 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.LIB. If not, 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_sub_ui (mpfr_ptr y, mpfr_srcptr x, unsigned long int u, mp_rnd_t rnd_mode) |
| { |
| if (MPFR_LIKELY (u != 0)) /* if u=0, do nothing */ |
| { |
| mpfr_t uu; |
| mp_limb_t up[1]; |
| unsigned long cnt; |
| int inex; |
| |
| MPFR_SAVE_EXPO_DECL (expo); |
| |
| MPFR_TMP_INIT1 (up, uu, BITS_PER_MP_LIMB); |
| MPFR_ASSERTN (u == (mp_limb_t) u); |
| count_leading_zeros (cnt, (mp_limb_t) u); |
| *up = (mp_limb_t) u << cnt; |
| |
| /* Optimization note: Exponent save/restore operations may be |
| removed if mpfr_sub works even when uu is out-of-range. */ |
| MPFR_SAVE_EXPO_MARK (expo); |
| MPFR_SET_EXP (uu, BITS_PER_MP_LIMB - cnt); |
| inex = mpfr_sub (y, x, uu, rnd_mode); |
| MPFR_SAVE_EXPO_FREE (expo); |
| return mpfr_check_range (y, inex, rnd_mode); |
| } |
| else |
| return mpfr_set (y, x, rnd_mode); |
| } |