| /* mpfr_nextabove, mpfr_nextbelow, mpfr_nexttoward -- next representable |
| floating-point number |
| |
| Copyright 1999, 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. */ |
| |
| #include "mpfr-impl.h" |
| |
| void |
| mpfr_nexttozero (mpfr_ptr x) |
| { |
| if (MPFR_UNLIKELY(MPFR_IS_INF(x))) |
| { |
| MPFR_CLEAR_FLAGS(x); |
| mpfr_setmax (x, __gmpfr_emax); |
| return; |
| } |
| else if (MPFR_UNLIKELY( MPFR_IS_ZERO(x) )) |
| { |
| MPFR_CHANGE_SIGN(x); |
| mpfr_setmin (x, __gmpfr_emin); |
| } |
| else |
| { |
| mp_size_t xn; |
| int sh; |
| mp_limb_t *xp; |
| |
| xn = MPFR_LIMB_SIZE (x); |
| MPFR_UNSIGNED_MINUS_MODULO (sh, MPFR_PREC(x)); |
| xp = MPFR_MANT(x); |
| mpn_sub_1 (xp, xp, xn, MPFR_LIMB_ONE << sh); |
| if (MPFR_UNLIKELY( MPFR_LIMB_MSB(xp[xn-1]) == 0) ) |
| { /* was an exact power of two: not normalized any more */ |
| mp_exp_t exp = MPFR_EXP (x); |
| if (MPFR_UNLIKELY(exp == __gmpfr_emin)) |
| MPFR_SET_ZERO(x); |
| else |
| { |
| mp_size_t i; |
| MPFR_SET_EXP (x, exp - 1); |
| xp[0] = MP_LIMB_T_MAX << sh; |
| for (i = 1; i < xn; i++) |
| xp[i] = MP_LIMB_T_MAX; |
| } |
| } |
| } |
| } |
| |
| void |
| mpfr_nexttoinf (mpfr_ptr x) |
| { |
| if (MPFR_UNLIKELY(MPFR_IS_INF(x))) |
| return; |
| else if (MPFR_UNLIKELY(MPFR_IS_ZERO(x))) |
| mpfr_setmin (x, __gmpfr_emin); |
| else |
| { |
| mp_size_t xn; |
| int sh; |
| mp_limb_t *xp; |
| |
| xn = MPFR_LIMB_SIZE (x); |
| MPFR_UNSIGNED_MINUS_MODULO (sh, MPFR_PREC(x)); |
| xp = MPFR_MANT(x); |
| if (MPFR_UNLIKELY( mpn_add_1 (xp, xp, xn, MPFR_LIMB_ONE << sh)) ) |
| /* got 1.0000... */ |
| { |
| mp_exp_t exp = MPFR_EXP (x); |
| if (MPFR_UNLIKELY(exp == __gmpfr_emax)) |
| MPFR_SET_INF(x); |
| else |
| { |
| MPFR_SET_EXP (x, exp + 1); |
| xp[xn-1] = MPFR_LIMB_HIGHBIT; |
| } |
| } |
| } |
| } |
| |
| void |
| mpfr_nextabove (mpfr_ptr x) |
| { |
| if (MPFR_UNLIKELY(MPFR_IS_NAN(x))) |
| { |
| __gmpfr_flags |= MPFR_FLAGS_NAN; |
| return; |
| } |
| if (MPFR_IS_NEG(x)) |
| mpfr_nexttozero (x); |
| else |
| mpfr_nexttoinf (x); |
| } |
| |
| void |
| mpfr_nextbelow (mpfr_ptr x) |
| { |
| if (MPFR_UNLIKELY(MPFR_IS_NAN(x))) |
| { |
| __gmpfr_flags |= MPFR_FLAGS_NAN; |
| return; |
| } |
| |
| if (MPFR_IS_NEG(x)) |
| mpfr_nexttoinf (x); |
| else |
| mpfr_nexttozero (x); |
| } |
| |
| void |
| mpfr_nexttoward (mpfr_ptr x, mpfr_srcptr y) |
| { |
| int s; |
| |
| if (MPFR_UNLIKELY(MPFR_IS_NAN(x))) |
| { |
| __gmpfr_flags |= MPFR_FLAGS_NAN; |
| return; |
| } |
| else if (MPFR_UNLIKELY(MPFR_IS_NAN(x) || MPFR_IS_NAN(y))) |
| { |
| MPFR_SET_NAN(x); |
| __gmpfr_flags |= MPFR_FLAGS_NAN; |
| return; |
| } |
| |
| s = mpfr_cmp (x, y); |
| if (s == 0) |
| return; |
| else if (s < 0) |
| mpfr_nextabove (x); |
| else |
| mpfr_nextbelow (x); |
| } |