source/libs/mpfr/mpfr-3.1.3/src/add.c

   1 /* mpfr_add -- add two floating-point numbers
   2
   3 Copyright 1999-2004, 2006-2015 Free Software Foundation, Inc.
   4 Contributed by the AriC 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 #include "mpfr-impl.h"
  24
  25 int
  26 mpfr_add (mpfr_ptr a, mpfr_srcptr b, mpfr_srcptr c, mpfr_rnd_t rnd_mode)
  27 {
  28   MPFR_LOG_FUNC
  29     (("b[%Pu]=%.*Rg c[%Pu]=%.*Rg rnd=%d",
  30       mpfr_get_prec (b), mpfr_log_prec, b,
  31       mpfr_get_prec (c), mpfr_log_prec, c, rnd_mode),
  32      ("a[%Pu]=%.*Rg", mpfr_get_prec (a), mpfr_log_prec, a));
  33
  34   if (MPFR_ARE_SINGULAR(b,c))
  35     {
  36       if (MPFR_IS_NAN(b) || MPFR_IS_NAN(c))
  37         {
  38           MPFR_SET_NAN(a);
  39           MPFR_RET_NAN;
  40         }
  41       /* neither b nor c is NaN here */
  42       else if (MPFR_IS_INF(b))
  43         {
  44           if (!MPFR_IS_INF(c) || MPFR_SIGN(b) == MPFR_SIGN(c))
  45             {
  46               MPFR_SET_INF(a);
  47               MPFR_SET_SAME_SIGN(a, b);
  48               MPFR_RET(0); /* exact */
  49             }
  50           else
  51             {
  52               MPFR_SET_NAN(a);
  53               MPFR_RET_NAN;
  54             }
  55         }
  56       else if (MPFR_IS_INF(c))
  57           {
  58             MPFR_SET_INF(a);
  59             MPFR_SET_SAME_SIGN(a, c);
  60             MPFR_RET(0); /* exact */
  61           }
  62       /* now either b or c is zero */
  63       else if (MPFR_IS_ZERO(b))
  64         {
  65           if (MPFR_IS_ZERO(c))
  66             {
  67               /* for round away, we take the same convention for 0 + 0
  68                  as for round to zero or to nearest: it always gives +0,
  69                  except (-0) + (-0) = -0. */
  70               MPFR_SET_SIGN(a,
  71                             (rnd_mode != MPFR_RNDD ?
  72                              ((MPFR_IS_NEG(b) && MPFR_IS_NEG(c)) ? -1 : 1) :
  73                              ((MPFR_IS_POS(b) && MPFR_IS_POS(c)) ? 1 : -1)));
  74               MPFR_SET_ZERO(a);
  75               MPFR_RET(0); /* 0 + 0 is exact */
  76             }
  77           return mpfr_set (a, c, rnd_mode);
  78         }
  79       else
  80         {
  81           MPFR_ASSERTD(MPFR_IS_ZERO(c));
  82           return mpfr_set (a, b, rnd_mode);
  83         }
  84     }
  85
  86   MPFR_ASSERTD (MPFR_IS_PURE_FP (b));
  87   MPFR_ASSERTD (MPFR_IS_PURE_FP (c));
  88
  89   if (MPFR_UNLIKELY(MPFR_SIGN(b) != MPFR_SIGN(c)))
  90     { /* signs differ, it is a subtraction */
  91       if (MPFR_LIKELY(MPFR_PREC(a) == MPFR_PREC(b)
  92                       && MPFR_PREC(b) == MPFR_PREC(c)))
  93         return mpfr_sub1sp(a, b, c, rnd_mode);
  94       else
  95         return mpfr_sub1(a, b, c, rnd_mode);
  96     }
  97   else
  98     { /* signs are equal, it's an addition */
  99       if (MPFR_LIKELY(MPFR_PREC(a) == MPFR_PREC(b)
 100                       && MPFR_PREC(b) == MPFR_PREC(c)))
 101         if (MPFR_GET_EXP(b) < MPFR_GET_EXP(c))
 102           return mpfr_add1sp(a, c, b, rnd_mode);
 103         else
 104           return mpfr_add1sp(a, b, c, rnd_mode);
 105       else
 106         if (MPFR_GET_EXP(b) < MPFR_GET_EXP(c))
 107           return mpfr_add1(a, c, b, rnd_mode);
 108         else
 109           return mpfr_add1(a, b, c, rnd_mode);
 110     }
 111 }