xref: /dragonfly/contrib/mpfr/src/add.c (revision 6e278935)
1 /* mpfr_add -- add two floating-point numbers
2 
3 Copyright 1999, 2000, 2001, 2002, 2003, 2004, 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
4 Contributed by the Arenaire 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 }
112