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/* mpfr_ui_sub -- subtract a floating-point number from an integer
Copyright 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
This file is part of the MPFR Library.
The 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 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 MPFR Library; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA. */
#define MPFR_NEED_LONGLONG_H
#include "mpfr-impl.h"
int
mpfr_ui_sub (mpfr_ptr y, unsigned long int u, mpfr_srcptr x, mp_rnd_t rnd_mode)
{
mpfr_t uu;
mp_limb_t up[1];
unsigned long cnt;
if (MPFR_UNLIKELY(MPFR_IS_SINGULAR(x)))
{
if (MPFR_IS_NAN(x))
{
MPFR_SET_NAN(y);
MPFR_RET_NAN;
}
else 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 */
}
else /* x is zero */
/* u - 0 = u */
return mpfr_set_ui(y, u, rnd_mode);
}
else if (MPFR_LIKELY(u))
{
MPFR_TMP_INIT1 (up, uu, BITS_PER_MP_LIMB);
MPFR_ASSERTN(u == (mp_limb_t) u);
count_leading_zeros (cnt, (mp_limb_t) u);
*up = (mp_limb_t) u << cnt;
MPFR_SET_EXP (uu, BITS_PER_MP_LIMB - cnt);
return mpfr_sub (y, uu, x, rnd_mode);
}
else
/* u == 0 BUT x != 0 */
return mpfr_neg (y, x, rnd_mode); /* if u=0, then set y to -x */
}
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