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/* mpfr_set_q -- set a floating-point number from a multiple-precision rational
Copyright 2000, 2001, 2002, 2004, 2005 Free Software Foundation, Inc.
This file is part of the MPFR Library.
The MPFR Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or (at your
option) any later version.
The MPFR Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
License for more details.
You should have received a copy of the GNU Lesser General Public License
along with the MPFR Library; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 51 Franklin Place, Fifth Floor, Boston,
MA 02110-1301, USA. */
#define MPFR_NEED_LONGLONG_H
#include "mpfr-impl.h"
/*
* Set f to z, choosing the smallest precision for f
* so that z = f*(2^BPML)*zs*2^(RetVal)
*/
static int
set_z (mpfr_ptr f, mpz_srcptr z, mp_size_t *zs)
{
mp_limb_t *p;
mp_size_t s;
int c;
mp_prec_t pf;
MPFR_ASSERTD (mpz_sgn (z) != 0);
/* Remove useless ending 0 */
for (p = PTR (z), s = *zs = ABS (SIZ (z)) ; *p == 0; p++, s--)
MPFR_ASSERTD (s >= 0);
/* Get working precision */
count_leading_zeros (c, p[s-1]);
pf = s * BITS_PER_MP_LIMB - c;
if (pf < MPFR_PREC_MIN)
pf = MPFR_PREC_MIN;
mpfr_init2 (f, pf);
/* Copy Mantissa */
if (MPFR_LIKELY (c))
mpn_lshift (MPFR_MANT (f), p, s, c);
else
MPN_COPY (MPFR_MANT (f), p, s);
MPFR_SET_SIGN (f, mpz_sgn (z));
MPFR_SET_EXP (f, 0);
return -c;
}
/* set f to the rational q */
int
mpfr_set_q (mpfr_ptr f, mpq_srcptr q, mp_rnd_t rnd)
{
mpz_srcptr num, den;
mpfr_t n, d;
int inexact;
int cn, cd;
long shift;
mp_size_t sn, sd;
MPFR_SAVE_EXPO_DECL (expo);
num = mpq_numref (q);
den = mpq_denref (q);
/* NAN and INF for mpq are not really documented, but could be found */
if (MPFR_UNLIKELY (mpz_sgn (num) == 0))
{
if (MPFR_UNLIKELY (mpz_sgn (den) == 0))
{
MPFR_SET_NAN (f);
MPFR_RET_NAN;
}
else
{
MPFR_SET_ZERO (f);
MPFR_SET_POS (f);
MPFR_RET (0);
}
}
if (MPFR_UNLIKELY (mpz_sgn (den) == 0))
{
MPFR_SET_INF (f);
MPFR_SET_SIGN (f, mpz_sgn (num));
MPFR_RET (0);
}
MPFR_SAVE_EXPO_MARK (expo);
cn = set_z (n, num, &sn);
cd = set_z (d, den, &sd);
sn -= sd;
if (MPFR_UNLIKELY (sn > MPFR_EMAX_MAX / BITS_PER_MP_LIMB))
{
inexact = mpfr_overflow (f, rnd, MPFR_SIGN (f));
goto end;
}
if (MPFR_UNLIKELY (sn < MPFR_EMIN_MIN / BITS_PER_MP_LIMB -1))
{
if (rnd == GMP_RNDN)
rnd = GMP_RNDZ;
inexact = mpfr_underflow (f, rnd, MPFR_SIGN (f));
goto end;
}
inexact = mpfr_div (f, n, d, rnd);
shift = BITS_PER_MP_LIMB*sn+cn-cd;
MPFR_ASSERTD (shift == BITS_PER_MP_LIMB*sn+cn-cd);
cd = mpfr_mul_2si (f, f, shift, rnd);
MPFR_SAVE_EXPO_FREE (expo);
if (MPFR_UNLIKELY (cd != 0))
inexact = cd;
else
inexact = mpfr_check_range (f, inexact, rnd);
end:
mpfr_clear (d);
mpfr_clear (n);
return inexact;
}
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