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/* mpfr_ui_sub -- subtract a floating-point number from an integer
Copyright 2000-2021 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. */
#define MPFR_NEED_LONGLONG_H
#include "mpfr-impl.h"
int
mpfr_ui_sub (mpfr_ptr y, unsigned long int u, mpfr_srcptr x, mpfr_rnd_t rnd_mode)
{
MPFR_LOG_FUNC
(("u=%lu x[%Pu]=%.*Rg rnd=%d",
u, mpfr_get_prec(x), mpfr_log_prec, x, rnd_mode),
("y[%Pu]=%.*Rg", mpfr_get_prec(y), mpfr_log_prec, y));
/* (unsigned long) 0 is assumed to be a real 0 (unsigned) */
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;
}
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 */
}
MPFR_ASSERTD (MPFR_IS_ZERO (x) && u != 0);
/* Note: the fact that u != 0 is important due to signed zeros. */
/* u - 0 = u */
return mpfr_set_ui (y, u, rnd_mode);
}
/* Main code */
{
int inex;
MPFR_SAVE_EXPO_DECL (expo);
/* Optimization note: Exponent save/restore operations may be
removed if mpfr_sub works even when uu is out-of-range. */
MPFR_SAVE_EXPO_MARK (expo);
#ifdef MPFR_LONG_WITHIN_LIMB
{
mpfr_t uu;
mp_limb_t up[1];
int cnt;
MPFR_TMP_INIT1 (up, uu, GMP_NUMB_BITS);
/* So, u fits in a mp_limb_t, which justifies the casts below. */
MPFR_ASSERTD (u != 0);
count_leading_zeros (cnt, (mp_limb_t) u);
up[0] = (mp_limb_t) u << cnt;
MPFR_SET_EXP (uu, GMP_NUMB_BITS - cnt);
inex = mpfr_sub (y, uu, x, rnd_mode);
}
#else
{
mpfr_t uu;
mpfr_init2 (uu, sizeof (unsigned long) * CHAR_BIT);
mpfr_set_ui (uu, u, MPFR_RNDZ);
inex = mpfr_sub (y, uu, x, rnd_mode);
mpfr_clear (uu);
}
#endif
MPFR_SAVE_EXPO_UPDATE_FLAGS (expo, __gmpfr_flags);
MPFR_SAVE_EXPO_FREE (expo);
return mpfr_check_range (y, inex, rnd_mode);
}
}
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