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152 lines
3.6 KiB
C
152 lines
3.6 KiB
C
/* mpfr_nextabove, mpfr_nextbelow, mpfr_nexttoward -- next representable
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floating-point number
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Copyright 1999, 2001, 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
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Contributed by the Arenaire and Cacao projects, INRIA.
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This file is part of the MPFR Library.
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The MPFR Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or (at your
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option) any later version.
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The MPFR Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the MPFR Library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
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MA 02110-1301, USA. */
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#include "mpfr-impl.h"
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void
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mpfr_nexttozero (mpfr_ptr x)
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{
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if (MPFR_UNLIKELY(MPFR_IS_INF(x)))
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{
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MPFR_CLEAR_FLAGS(x);
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mpfr_setmax (x, __gmpfr_emax);
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return;
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}
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else if (MPFR_UNLIKELY( MPFR_IS_ZERO(x) ))
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{
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MPFR_CHANGE_SIGN(x);
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mpfr_setmin (x, __gmpfr_emin);
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}
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else
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{
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mp_size_t xn;
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int sh;
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mp_limb_t *xp;
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xn = MPFR_LIMB_SIZE (x);
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MPFR_UNSIGNED_MINUS_MODULO (sh, MPFR_PREC(x));
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xp = MPFR_MANT(x);
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mpn_sub_1 (xp, xp, xn, MPFR_LIMB_ONE << sh);
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if (MPFR_UNLIKELY( MPFR_LIMB_MSB(xp[xn-1]) == 0) )
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{ /* was an exact power of two: not normalized any more */
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mp_exp_t exp = MPFR_EXP (x);
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if (MPFR_UNLIKELY(exp == __gmpfr_emin))
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MPFR_SET_ZERO(x);
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else
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{
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mp_size_t i;
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MPFR_SET_EXP (x, exp - 1);
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xp[0] = MP_LIMB_T_MAX << sh;
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for (i = 1; i < xn; i++)
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xp[i] = MP_LIMB_T_MAX;
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}
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}
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}
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}
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void
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mpfr_nexttoinf (mpfr_ptr x)
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{
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if (MPFR_UNLIKELY(MPFR_IS_INF(x)))
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return;
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else if (MPFR_UNLIKELY(MPFR_IS_ZERO(x)))
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mpfr_setmin (x, __gmpfr_emin);
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else
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{
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mp_size_t xn;
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int sh;
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mp_limb_t *xp;
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xn = MPFR_LIMB_SIZE (x);
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MPFR_UNSIGNED_MINUS_MODULO (sh, MPFR_PREC(x));
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xp = MPFR_MANT(x);
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if (MPFR_UNLIKELY( mpn_add_1 (xp, xp, xn, MPFR_LIMB_ONE << sh)) )
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/* got 1.0000... */
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{
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mp_exp_t exp = MPFR_EXP (x);
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if (MPFR_UNLIKELY(exp == __gmpfr_emax))
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MPFR_SET_INF(x);
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else
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{
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MPFR_SET_EXP (x, exp + 1);
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xp[xn-1] = MPFR_LIMB_HIGHBIT;
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}
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}
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}
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}
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void
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mpfr_nextabove (mpfr_ptr x)
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{
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if (MPFR_UNLIKELY(MPFR_IS_NAN(x)))
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{
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__gmpfr_flags |= MPFR_FLAGS_NAN;
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return;
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}
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if (MPFR_IS_NEG(x))
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mpfr_nexttozero (x);
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else
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mpfr_nexttoinf (x);
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}
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void
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mpfr_nextbelow (mpfr_ptr x)
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{
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if (MPFR_UNLIKELY(MPFR_IS_NAN(x)))
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{
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__gmpfr_flags |= MPFR_FLAGS_NAN;
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return;
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}
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if (MPFR_IS_NEG(x))
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mpfr_nexttoinf (x);
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else
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mpfr_nexttozero (x);
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}
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void
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mpfr_nexttoward (mpfr_ptr x, mpfr_srcptr y)
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{
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int s;
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if (MPFR_UNLIKELY(MPFR_IS_NAN(x)))
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{
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__gmpfr_flags |= MPFR_FLAGS_NAN;
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return;
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}
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else if (MPFR_UNLIKELY(MPFR_IS_NAN(x) || MPFR_IS_NAN(y)))
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{
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MPFR_SET_NAN(x);
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__gmpfr_flags |= MPFR_FLAGS_NAN;
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return;
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}
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s = mpfr_cmp (x, y);
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if (s == 0)
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return;
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else if (s < 0)
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mpfr_nextabove (x);
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else
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mpfr_nextbelow (x);
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}
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