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/* mpfr_nextabove, mpfr_nextbelow, mpfr_nexttoward -- next representable
floating-point number
Copyright 1999, 2001-2019 Free Software Foundation, Inc.
Contributed by the AriC and Caramba 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 3 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.LESSER. If not, see
https://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
/* Note concerning the exceptions: In case of NaN result, the NaN flag is
* set as usual. No underflow or overflow is generated (this contradicts
* the obsolete IEEE 754-1985 standard for Nextafter, but conforms to the
* current standard IEEE 754-2008 for nextUp and nextDown).
*/
#include "mpfr-impl.h"
void
mpfr_nexttozero (mpfr_ptr x)
{
if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (x)))
{
if (MPFR_IS_INF (x))
{
mpfr_setmax (x, __gmpfr_emax);
}
else
{
MPFR_ASSERTN (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,
thus do not use MPFR_GET_EXP. */
mpfr_exp_t exp = MPFR_EXP (x);
if (MPFR_UNLIKELY (exp == __gmpfr_emin))
MPFR_SET_ZERO(x);
else
{
MPFR_SET_EXP (x, exp - 1);
/* The following is valid whether xn = 1 or xn > 1. */
xp[xn-1] |= MPFR_LIMB_HIGHBIT;
}
}
}
}
void
mpfr_nexttoinf (mpfr_ptr x)
{
if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (x)))
{
if (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... */
{
mpfr_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);
}
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