/* mpfr_add -- add two floating-point numbers

Copyright 1999, 2000, 2001, 2002 Free Software Foundation.
Contributed by the Spaces project, INRIA Lorraine.

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., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA. */

#include "gmp.h"
#include "gmp-impl.h"
#include "mpfr.h"
#include "mpfr-impl.h"

int
mpfr_add (mpfr_ptr a, mpfr_srcptr b, mpfr_srcptr c, mp_rnd_t rnd_mode)
{
  if (MPFR_IS_NAN(b) || MPFR_IS_NAN(c))
    {
      MPFR_SET_NAN(a);
      MPFR_RET_NAN;
    }

  MPFR_CLEAR_NAN(a);

  if (MPFR_IS_INF(b))
    {
      if (!MPFR_IS_INF(c) || MPFR_SIGN(b) == MPFR_SIGN(c))
        {
          MPFR_SET_INF(a);
          MPFR_SET_SAME_SIGN(a, b);
          MPFR_RET(0); /* exact */
        }
      else
        {
          MPFR_SET_NAN(a);
          MPFR_RET_NAN;
        }
    }
  else
    if (MPFR_IS_INF(c))
      {
        MPFR_SET_INF(a);
        MPFR_SET_SAME_SIGN(a, c);
        MPFR_RET(0); /* exact */
      }

  MPFR_ASSERTN(MPFR_IS_FP(b) && MPFR_IS_FP(c));

  if (MPFR_IS_ZERO(b))
    {
      if (MPFR_IS_ZERO(c))
        {
          if (MPFR_SIGN(a) !=
              (rnd_mode != GMP_RNDD ?
               ((MPFR_SIGN(b) < 0 && MPFR_SIGN(c) < 0) ? -1 : 1) :
               ((MPFR_SIGN(b) > 0 && MPFR_SIGN(c) > 0) ? 1 : -1)))
            {
              MPFR_CHANGE_SIGN(a);
            }
          MPFR_CLEAR_INF(a);
          MPFR_SET_ZERO(a);
          MPFR_RET(0); /* 0 + 0 is exact */
        }
      return mpfr_set(a, c, rnd_mode);
    }

  if (MPFR_IS_ZERO(c))
    {
      return mpfr_set(a, b, rnd_mode);
    }

  MPFR_CLEAR_INF(a); /* clear Inf flag */

  if (MPFR_SIGN(b) != MPFR_SIGN(c))
    { /* signs differ, it's a subtraction */
      return mpfr_sub1(a, b, c, rnd_mode, 0);
    }
  else
    { /* signs are equal, it's an addition */
      if (MPFR_EXP(b) < MPFR_EXP(c))
        {
          return mpfr_add1(a, c, b, rnd_mode,
                           (mp_exp_unsigned_t) MPFR_EXP(c) - MPFR_EXP(b));
        }
      else
        {
          return mpfr_add1(a, b, c, rnd_mode,
                           (mp_exp_unsigned_t) MPFR_EXP(b) - MPFR_EXP(c));
        }
    }
}