1 /* mpfr_set_q -- set a floating-point number from a multiple-precision rational 2 3 Copyright 2000, 2001, 2002, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc. 4 Contributed by the Arenaire and Caramel projects, INRIA. 5 6 This file is part of the GNU MPFR Library. 7 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. 12 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. 17 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. */ 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 */ 30 static int 31 set_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 */ 64 int 65 mpfr_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