1 /* mpfr_ui_sub -- subtract a floating-point number from an integer 2 3 Copyright 2000-2018 Free Software Foundation, Inc. 4 Contributed by the AriC and Caramba projects, INRIA. 5 6 This file is part of the GNU MPFR Library. 7 8 The GNU MPFR 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 MPFR 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 MPFR Library; see the file COPYING.LESSER. If not, see 20 http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc., 21 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */ 22 23 #define MPFR_NEED_LONGLONG_H 24 #include "mpfr-impl.h" 25 26 int 27 mpfr_ui_sub (mpfr_ptr y, unsigned long int u, mpfr_srcptr x, mpfr_rnd_t rnd_mode) 28 { 29 MPFR_LOG_FUNC 30 (("u=%lu x[%Pu]=%.*Rg rnd=%d", 31 u, mpfr_get_prec(x), mpfr_log_prec, x, rnd_mode), 32 ("y[%Pu]=%.*Rg", mpfr_get_prec(y), mpfr_log_prec, y)); 33 34 /* (unsigned long) 0 is assumed to be a real 0 (unsigned) */ 35 if (MPFR_UNLIKELY (u == 0)) 36 return mpfr_neg (y, x, rnd_mode); 37 38 if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (x))) 39 { 40 if (MPFR_IS_NAN (x)) 41 { 42 MPFR_SET_NAN (y); 43 MPFR_RET_NAN; 44 } 45 if (MPFR_IS_INF (x)) 46 { 47 /* u - Inf = -Inf and u - -Inf = +Inf */ 48 MPFR_SET_INF (y); 49 MPFR_SET_OPPOSITE_SIGN (y, x); 50 MPFR_RET (0); /* +/-infinity is exact */ 51 } 52 MPFR_ASSERTD (MPFR_IS_ZERO (x) && u != 0); 53 /* Note: the fact that u != 0 is important due to signed zeros. */ 54 /* u - 0 = u */ 55 return mpfr_set_ui (y, u, rnd_mode); 56 } 57 58 /* Main code */ 59 { 60 mpfr_t uu; 61 mp_limb_t up[1]; 62 int cnt; 63 int inex; 64 MPFR_SAVE_EXPO_DECL (expo); 65 66 MPFR_TMP_INIT1 (up, uu, GMP_NUMB_BITS); 67 MPFR_STAT_STATIC_ASSERT (MPFR_LIMB_MAX >= ULONG_MAX); 68 /* So, u fits in a mp_limb_t, which justifies the casts below. */ 69 MPFR_ASSERTD (u != 0); 70 count_leading_zeros (cnt, (mp_limb_t) u); 71 up[0] = (mp_limb_t) u << cnt; 72 73 /* Optimization note: Exponent save/restore operations may be 74 removed if mpfr_sub works even when uu is out-of-range. */ 75 MPFR_SAVE_EXPO_MARK (expo); 76 MPFR_SET_EXP (uu, GMP_NUMB_BITS - cnt); 77 inex = mpfr_sub (y, uu, x, rnd_mode); 78 MPFR_SAVE_EXPO_UPDATE_FLAGS (expo, __gmpfr_flags); 79 MPFR_SAVE_EXPO_FREE (expo); 80 return mpfr_check_range (y, inex, rnd_mode); 81 } 82 } 83