Annotation of OpenXM_contrib/gmp/mpfr/add_one_ulp.c, Revision 1.1.1.1
1.1 ohara 1: /* mpfr_add_one_ulp -- add one unit in last place
2:
3: Copyright 1999, 2001 Free Software Foundation, Inc.
4:
5: This file is part of the MPFR Library.
6:
7: The MPFR Library is free software; you can redistribute it and/or modify
8: it under the terms of the GNU Lesser General Public License as published by
9: the Free Software Foundation; either version 2.1 of the License, or (at your
10: option) any later version.
11:
12: The MPFR Library is distributed in the hope that it will be useful, but
13: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
14: or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
15: License for more details.
16:
17: You should have received a copy of the GNU Lesser General Public License
18: along with the MPFR Library; see the file COPYING.LIB. If not, write to
19: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
20: MA 02111-1307, USA. */
21:
22: #include "gmp.h"
23: #include "gmp-impl.h"
24: #include "mpfr.h"
25: #include "mpfr-impl.h"
26:
27: /* sets x to x+sign(x)*ulp(x) */
28: int
29: mpfr_add_one_ulp (mpfr_ptr x, mp_rnd_t rnd_mode)
30: {
31: mp_size_t xn;
32: int sh;
33: mp_limb_t *xp;
34:
35: if (MPFR_IS_NAN(x))
36: MPFR_RET_NAN;
37:
38: if (MPFR_IS_INF(x) || MPFR_IS_ZERO(x))
39: return 0;
40:
41: xn = 1 + (MPFR_PREC(x) - 1) / BITS_PER_MP_LIMB;
42: sh = xn * BITS_PER_MP_LIMB - MPFR_PREC(x);
43: xp = MPFR_MANT(x);
44: if (mpn_add_1 (xp, xp, xn, MP_LIMB_T_ONE << sh)) /* got 1.0000... */
45: {
46: mp_exp_t exp = MPFR_EXP(x);
47: if (exp == __mpfr_emax)
48: return mpfr_set_overflow(x, rnd_mode, MPFR_SIGN(x));
49: else
50: {
51: MPFR_EXP(x)++;
52: xp[xn-1] = GMP_LIMB_HIGHBIT;
53: }
54: }
55: return 0;
56: }
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