1 /* mpfr_ui_sub -- subtract a floating-point number from an integer
3 Copyright 2000-2015 Free Software Foundation, Inc.
4 Contributed by the AriC and Caramel projects, INRIA.
6 This file is part of the GNU MPFR Library.
8 The GNU MPFR Library is free software; you can redistribute it and/or modify
9 it under the terms of the GNU Lesser General Public License as published by
10 the Free Software Foundation; either version 3 of the License, or (at your
11 option) any later version.
13 The GNU MPFR Library is distributed in the hope that it will be useful, but
14 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
15 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
16 License for more details.
18 You should have received a copy of the GNU Lesser General Public License
19 along with the GNU MPFR Library; see the file COPYING.LESSER. If not, see
20 http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
21 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
23 #define MPFR_NEED_LONGLONG_H
24 #include "mpfr-impl.h"
27 mpfr_ui_sub (mpfr_ptr y
, unsigned long int u
, mpfr_srcptr x
, mpfr_rnd_t rnd_mode
)
30 (("u=%lu x[%Pu]=%.*Rg rnd=%d",
31 u
, mpfr_get_prec(x
), mpfr_log_prec
, x
, rnd_mode
),
32 ("y[%Pu]=%.*Rg", mpfr_get_prec(y
), mpfr_log_prec
, y
));
34 if (MPFR_UNLIKELY (u
== 0))
35 return mpfr_neg (y
, x
, rnd_mode
);
37 if (MPFR_UNLIKELY(MPFR_IS_SINGULAR(x
)))
44 else if (MPFR_IS_INF(x
))
46 /* u - Inf = -Inf and u - -Inf = +Inf */
48 MPFR_SET_OPPOSITE_SIGN(y
,x
);
49 MPFR_RET(0); /* +/-infinity is exact */
53 return mpfr_set_ui(y
, u
, rnd_mode
);
62 MPFR_SAVE_EXPO_DECL (expo
);
64 MPFR_TMP_INIT1 (up
, uu
, GMP_NUMB_BITS
);
65 MPFR_ASSERTN(u
== (mp_limb_t
) u
);
66 count_leading_zeros (cnt
, (mp_limb_t
) u
);
67 up
[0] = (mp_limb_t
) u
<< cnt
;
69 /* Optimization note: Exponent save/restore operations may be
70 removed if mpfr_sub works even when uu is out-of-range. */
71 MPFR_SAVE_EXPO_MARK (expo
);
72 MPFR_SET_EXP (uu
, GMP_NUMB_BITS
- cnt
);
73 inex
= mpfr_sub (y
, uu
, x
, rnd_mode
);
74 MPFR_SAVE_EXPO_UPDATE_FLAGS (expo
, __gmpfr_flags
);
75 MPFR_SAVE_EXPO_FREE (expo
);
76 return mpfr_check_range(y
, inex
, rnd_mode
);