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/* mpfr_sub_ui -- subtract a floating-point number and a machine integer
Copyright (C) 2000, 2001 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. */
#include <stdio.h>
#include "gmp.h"
#include "gmp-impl.h"
#include "longlong.h"
#include "mpfr.h"
#include "mpfr-impl.h"
int
mpfr_sub_ui (mpfr_ptr y, mpfr_srcptr x, unsigned long int u, mp_rnd_t rnd_mode)
{
if (u) /* if u=0, do nothing */
{
mpfr_t uu;
mp_limb_t up[1];
unsigned long cnt;
int inex_sub, inex_cr;
MPFR_INIT1(up, uu, BITS_PER_MP_LIMB, 1);
count_leading_zeros(cnt, (mp_limb_t) u);
*up = (mp_limb_t) u << cnt;
MPFR_EXP(uu) = BITS_PER_MP_LIMB-cnt;
/* Optimization note: Exponent operations may be removed
if mpfr_add works even when uu is out-of-range. */
mpfr_save_emin_emax();
inex_sub = mpfr_sub (y, x, uu, rnd_mode);
mpfr_restore_emin_emax();
inex_cr = mpfr_check_range(y, rnd_mode);
if (inex_cr)
return inex_cr; /* underflow or overflow */
MPFR_RET(inex_sub);
}
else
return mpfr_set (y, x, rnd_mode);
}
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