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