| /* mpfr_ui_sub -- subtract a floating-point number from an 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_ui_sub (mpfr_ptr y, unsigned long int u, mpfr_srcptr x, mp_rnd_t rnd_mode) |
| { |
| mpfr_t uu; |
| mp_limb_t up[1]; |
| unsigned long cnt; |
| |
| if (MPFR_UNLIKELY (u == 0)) |
| return mpfr_neg (y, x, rnd_mode); |
| |
| if (MPFR_UNLIKELY(MPFR_IS_SINGULAR(x))) |
| { |
| if (MPFR_IS_NAN(x)) |
| { |
| MPFR_SET_NAN(y); |
| MPFR_RET_NAN; |
| } |
| else if (MPFR_IS_INF(x)) |
| { |
| /* u - Inf = -Inf and u - -Inf = +Inf */ |
| MPFR_SET_INF(y); |
| MPFR_SET_OPPOSITE_SIGN(y,x); |
| MPFR_RET(0); /* +/-infinity is exact */ |
| } |
| else /* x is zero */ |
| /* u - 0 = u */ |
| return mpfr_set_ui(y, u, rnd_mode); |
| } |
| else |
| { |
| 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; |
| MPFR_SET_EXP (uu, BITS_PER_MP_LIMB - cnt); |
| return mpfr_sub (y, uu, x, rnd_mode); |
| } |
| } |