mpfr-2.4.1/set.c

/* mpfr_set -- copy of a floating-point number

Copyright 1999, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
Contributed by the Arenaire and Cacao projects, INRIA.

This file is part of the GNU MPFR Library.

The GNU 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 GNU 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 GNU MPFR Library; see the file COPYING.LIB.  If not, write to
the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
MA 02110-1301, USA. */

#include "mpfr-impl.h"

/* set a to abs(b) * signb: a=b when signb = SIGN(b), a=abs(b) when signb=1 */
int
mpfr_set4 (mpfr_ptr a, mpfr_srcptr b, mp_rnd_t rnd_mode, int signb)
{
  /* Sign is ALWAYS copied */
  MPFR_SET_SIGN (a, signb);

  /* Exponent is also always copied since if the number is singular,
     the exponent field determined the number.
     Can't use MPFR_SET_EXP since the exponent may be singular */
  MPFR_EXP (a) = MPFR_EXP (b);

  if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (b)))
    {
      /* MPFR_SET_NAN, MPFR_SET_ZERO and MPFR_SET_INF are useless
         since MPFR_EXP (a) = MPFR_EXP (b) does the job */
      if (MPFR_IS_NAN (b))
        MPFR_RET_NAN;
      else
        MPFR_RET (0);
    }
  else if (MPFR_LIKELY (MPFR_PREC (b) == MPFR_PREC (a)))
    {
      /* Same precision and b is not singular:
       * just copy the mantissa, and set the exponent and the sign
       * The result is exact. */
      MPN_COPY (MPFR_MANT (a), MPFR_MANT (b),
                (MPFR_PREC (b) + BITS_PER_MP_LIMB-1)/BITS_PER_MP_LIMB);
      MPFR_RET (0);
    }
  else
    {
      int inex;

      /* Else Round B inside a */
      MPFR_RNDRAW (inex, a, MPFR_MANT (b), MPFR_PREC (b), rnd_mode, signb,
                   if (MPFR_UNLIKELY ( ++MPFR_EXP (a) > __gmpfr_emax))
                    return mpfr_overflow (a, rnd_mode, signb) );
      MPFR_RET (inex);
    }
}

/* Set a to b  */
#undef mpfr_set
int
mpfr_set (mpfr_ptr a, mpfr_srcptr b, mp_rnd_t rnd_mode)
{
  return mpfr_set4 (a, b, rnd_mode, MPFR_SIGN (b));
}

/* Set a to |b| */
#undef mpfr_abs
int
mpfr_abs (mpfr_ptr a, mpfr_srcptr b, mp_rnd_t rnd_mode)
{
  return mpfr_set4 (a, b, rnd_mode, MPFR_SIGN_POS);
}