1/* mpfr_set_q -- set a floating-point number from a multiple-precision rational
2
3Copyright 2000, 2001, 2002, 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
26/*
27 * Set f to z, choosing the smallest precision for f
28 * so that z = f*(2^BPML)*zs*2^(RetVal)
29 */
30static int
31set_z (mpfr_ptr f, mpz_srcptr z, mp_size_t *zs)
32{
33  mp_limb_t *p;
34  mp_size_t s;
35  int c;
36  mpfr_prec_t pf;
37
38  MPFR_ASSERTD (mpz_sgn (z) != 0);
39
40  /* Remove useless ending 0 */
41  for (p = PTR (z), s = *zs = ABS (SIZ (z)) ; *p == 0; p++, s--)
42    MPFR_ASSERTD (s >= 0);
43
44  /* Get working precision */
45  count_leading_zeros (c, p[s-1]);
46  pf = s * GMP_NUMB_BITS - c;
47  if (pf < MPFR_PREC_MIN)
48    pf = MPFR_PREC_MIN;
49  mpfr_init2 (f, pf);
50
51  /* Copy Mantissa */
52  if (MPFR_LIKELY (c))
53    mpn_lshift (MPFR_MANT (f), p, s, c);
54  else
55    MPN_COPY (MPFR_MANT (f), p, s);
56
57  MPFR_SET_SIGN (f, mpz_sgn (z));
58  MPFR_SET_EXP (f, 0);
59
60  return -c;
61}
62
63/* set f to the rational q */
64int
65mpfr_set_q (mpfr_ptr f, mpq_srcptr q, mpfr_rnd_t rnd)
66{
67  mpz_srcptr num, den;
68  mpfr_t n, d;
69  int inexact;
70  int cn, cd;
71  long shift;
72  mp_size_t sn, sd;
73  MPFR_SAVE_EXPO_DECL (expo);
74
75  num = mpq_numref (q);
76  den = mpq_denref (q);
77  /* NAN and INF for mpq are not really documented, but could be found */
78  if (MPFR_UNLIKELY (mpz_sgn (num) == 0))
79    {
80      if (MPFR_UNLIKELY (mpz_sgn (den) == 0))
81        {
82          MPFR_SET_NAN (f);
83          MPFR_RET_NAN;
84        }
85      else
86        {
87          MPFR_SET_ZERO (f);
88          MPFR_SET_POS (f);
89          MPFR_RET (0);
90        }
91    }
92  if (MPFR_UNLIKELY (mpz_sgn (den) == 0))
93    {
94      MPFR_SET_INF (f);
95      MPFR_SET_SIGN (f, mpz_sgn (num));
96      MPFR_RET (0);
97    }
98
99  MPFR_SAVE_EXPO_MARK (expo);
100
101  cn = set_z (n, num, &sn);
102  cd = set_z (d, den, &sd);
103
104  sn -= sd;
105  if (MPFR_UNLIKELY (sn > MPFR_EMAX_MAX / GMP_NUMB_BITS))
106    {
107      inexact = mpfr_overflow (f, rnd, MPFR_SIGN (f));
108      goto end;
109    }
110  if (MPFR_UNLIKELY (sn < MPFR_EMIN_MIN / GMP_NUMB_BITS -1))
111    {
112      if (rnd == MPFR_RNDN)
113        rnd = MPFR_RNDZ;
114      inexact = mpfr_underflow (f, rnd, MPFR_SIGN (f));
115      goto end;
116    }
117
118  inexact = mpfr_div (f, n, d, rnd);
119  shift = GMP_NUMB_BITS*sn+cn-cd;
120  MPFR_ASSERTD (shift == GMP_NUMB_BITS*sn+cn-cd);
121  cd = mpfr_mul_2si (f, f, shift, rnd);
122  MPFR_SAVE_EXPO_FREE (expo);
123  if (MPFR_UNLIKELY (cd != 0))
124    inexact = cd;
125  else
126    inexact = mpfr_check_range (f, inexact, rnd);
127 end:
128  mpfr_clear (d);
129  mpfr_clear (n);
130  return inexact;
131}
132
133
134