contrib/mpfr/add.c

   1 /* mpfr_add -- add two floating-point numbers
   2
   3 Copyright 1999, 2000, 2001, 2002, 2003, 2004, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
   4 Contributed by the Arenaire and Cacao 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 2.1 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.LIB.  If not, write to
  20 the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
  21 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, mp_rnd_t rnd_mode)
  27 {
  28   MPFR_LOG_FUNC (("b[%#R]=%R c[%#R]=%R rnd=%d", b, b, c, c, rnd_mode),
  29                  ("a[%#R]=%R", a, a));
  30
  31   if (MPFR_ARE_SINGULAR(b,c))
  32     {
  33       if (MPFR_IS_NAN(b) || MPFR_IS_NAN(c))
  34         {
  35           MPFR_SET_NAN(a);
  36           MPFR_RET_NAN;
  37         }
  38       /* neither b nor c is NaN here */
  39       else if (MPFR_IS_INF(b))
  40         {
  41           if (!MPFR_IS_INF(c) || MPFR_SIGN(b) == MPFR_SIGN(c))
  42             {
  43               MPFR_SET_INF(a);
  44               MPFR_SET_SAME_SIGN(a, b);
  45               MPFR_RET(0); /* exact */
  46             }
  47           else
  48             {
  49               MPFR_SET_NAN(a);
  50               MPFR_RET_NAN;
  51             }
  52         }
  53       else if (MPFR_IS_INF(c))
  54           {
  55             MPFR_SET_INF(a);
  56             MPFR_SET_SAME_SIGN(a, c);
  57             MPFR_RET(0); /* exact */
  58           }
  59       /* now either b or c is zero */
  60       else if (MPFR_IS_ZERO(b))
  61         {
  62           if (MPFR_IS_ZERO(c))
  63             {
  64               MPFR_SET_SIGN(a,
  65                             (rnd_mode != GMP_RNDD ?
  66                              ((MPFR_IS_NEG(b) && MPFR_IS_NEG(c)) ? -1 : 1) :
  67                              ((MPFR_IS_POS(b) && MPFR_IS_POS(c)) ? 1 : -1)));
  68               MPFR_SET_ZERO(a);
  69               MPFR_RET(0); /* 0 + 0 is exact */
  70             }
  71           return mpfr_set (a, c, rnd_mode);
  72         }
  73       else
  74         {
  75           MPFR_ASSERTD(MPFR_IS_ZERO(c));
  76           return mpfr_set (a, b, rnd_mode);
  77         }
  78     }
  79
  80   MPFR_ASSERTD(MPFR_IS_PURE_FP(b) && MPFR_IS_PURE_FP(c));
  81   MPFR_CLEAR_FLAGS(a); /* clear flags */
  82
  83   if (MPFR_UNLIKELY(MPFR_SIGN(b) != MPFR_SIGN(c)))
  84     { /* signs differ, it's a subtraction */
  85       if (MPFR_LIKELY(MPFR_PREC(a) == MPFR_PREC(b)
  86                       && MPFR_PREC(b) == MPFR_PREC(c)))
  87         return mpfr_sub1sp(a,b,c,rnd_mode);
  88       else
  89         return mpfr_sub1(a, b, c, rnd_mode);
  90     }
  91   else
  92     { /* signs are equal, it's an addition */
  93       if (MPFR_LIKELY(MPFR_PREC(a) == MPFR_PREC(b)
  94                       && MPFR_PREC(b) == MPFR_PREC(c)))
  95         if (MPFR_GET_EXP(b) < MPFR_GET_EXP(c))
  96           return mpfr_add1sp(a, c, b, rnd_mode);
  97         else
  98           return mpfr_add1sp(a, b, c, rnd_mode);
  99       else
 100         if (MPFR_GET_EXP(b) < MPFR_GET_EXP(c))
 101           return mpfr_add1(a, c, b, rnd_mode);
 102         else
 103           return mpfr_add1(a, b, c, rnd_mode);
 104     }
 105 }