/* mpfr_add -- add two floating-point numbers

Copyright 1999, 2000, 2001, 2002, 2003, 2004, 2006 Free Software Foundation, Inc.
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., 51 Franklin Place, Fifth Floor, Boston,
MA 02110-1301, USA. */

#include "mpfr-impl.h"

int
mpfr_add (mpfr_ptr a, mpfr_srcptr b, mpfr_srcptr c, mp_rnd_t rnd_mode)
{
  if (MPFR_ARE_SINGULAR(b,c))
    {
      if (MPFR_IS_NAN(b) || MPFR_IS_NAN(c))
        {
          MPFR_SET_NAN(a);
          MPFR_RET_NAN;
        }
      /* neither b nor c is NaN here */
      else 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 */
          }
      /* now either b or c is zero */
      else if (MPFR_IS_ZERO(b))
        {
          if (MPFR_IS_ZERO(c))
            {
              MPFR_SET_SIGN(a,
                            (rnd_mode != GMP_RNDD ?
                             ((MPFR_IS_NEG(b) && MPFR_IS_NEG(c)) ? -1 : 1) :
                             ((MPFR_IS_POS(b) && MPFR_IS_POS(c)) ? 1 : -1)));
              MPFR_SET_ZERO(a);
              MPFR_RET(0); /* 0 + 0 is exact */
            }
          return mpfr_set (a, c, rnd_mode);
        }
      else
        {
          MPFR_ASSERTD(MPFR_IS_ZERO(c));
          return mpfr_set (a, b, rnd_mode);
        }
    }

  MPFR_ASSERTD(MPFR_IS_PURE_FP(b) && MPFR_IS_PURE_FP(c));
  MPFR_CLEAR_FLAGS(a); /* clear flags */

  if (MPFR_UNLIKELY(MPFR_SIGN(b) != MPFR_SIGN(c)))
    { /* signs differ, it's a subtraction */
      if (MPFR_LIKELY(MPFR_PREC(a) == MPFR_PREC(b)
                      && MPFR_PREC(b) == MPFR_PREC(c)))
        return mpfr_sub1sp(a,b,c,rnd_mode);
      else
        return mpfr_sub1(a, b, c, rnd_mode);
    }
  else
    { /* signs are equal, it's an addition */
      if (MPFR_LIKELY(MPFR_PREC(a) == MPFR_PREC(b)
                      && MPFR_PREC(b) == MPFR_PREC(c)))
        if (MPFR_GET_EXP(b) < MPFR_GET_EXP(c))
          return mpfr_add1sp(a, c, b, rnd_mode);
        else
          return mpfr_add1sp(a, b, c, rnd_mode);
      else
        if (MPFR_GET_EXP(b) < MPFR_GET_EXP(c))
          return mpfr_add1(a, c, b, rnd_mode);
        else
          return mpfr_add1(a, b, c, rnd_mode);
    }
}