1/* mpfr_ui_sub -- subtract a floating-point number from an integer
2
3Copyright 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc.
4Contributed by the AriC and Caramel projects, INRIA.
5
6This file is part of the GNU MPFR Library.
7
8The GNU MPFR Library is free software; you can redistribute it and/or modify
9it under the terms of the GNU Lesser General Public License as published by
10the Free Software Foundation; either version 3 of the License, or (at your
11option) any later version.
12
13The GNU MPFR Library is distributed in the hope that it will be useful, but
14WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
15or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
16License for more details.
17
18You should have received a copy of the GNU Lesser General Public License
19along with the GNU MPFR Library; see the file COPYING.LESSER.  If not, see
20http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
2151 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
22
23#define MPFR_NEED_LONGLONG_H
24#include "mpfr-impl.h"
25
26int
27mpfr_ui_sub (mpfr_ptr y, unsigned long int u, mpfr_srcptr x, mpfr_rnd_t rnd_mode)
28{
29  mpfr_t uu;
30  mp_limb_t up[1];
31  unsigned long cnt;
32
33  MPFR_LOG_FUNC
34    (("u=%lu x[%Pu]=%.*Rg rnd=%d",
35      u, mpfr_get_prec(x), mpfr_log_prec, x, rnd_mode),
36     ("y[%Pu]=%.*Rg", mpfr_get_prec(y), mpfr_log_prec, y));
37
38  if (MPFR_UNLIKELY (u == 0))
39    return mpfr_neg (y, x, rnd_mode);
40
41  if (MPFR_UNLIKELY(MPFR_IS_SINGULAR(x)))
42    {
43      if (MPFR_IS_NAN(x))
44        {
45          MPFR_SET_NAN(y);
46          MPFR_RET_NAN;
47        }
48      else if (MPFR_IS_INF(x))
49        {
50          /*  u - Inf = -Inf and u - -Inf = +Inf  */
51          MPFR_SET_INF(y);
52          MPFR_SET_OPPOSITE_SIGN(y,x);
53          MPFR_RET(0); /* +/-infinity is exact */
54        }
55      else /* x is zero */
56        /* u - 0 = u */
57        return mpfr_set_ui(y, u, rnd_mode);
58    }
59  else
60    {
61      MPFR_TMP_INIT1 (up, uu, GMP_NUMB_BITS);
62      MPFR_ASSERTN(u == (mp_limb_t) u);
63      count_leading_zeros (cnt, (mp_limb_t) u);
64      *up = (mp_limb_t) u << cnt;
65      MPFR_SET_EXP (uu, GMP_NUMB_BITS - cnt);
66      return mpfr_sub (y, uu, x, rnd_mode);
67    }
68}
69