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