contrib/mpfr/set.c

   1 /* mpfr_set -- copy of a floating-point number
   2
   3 Copyright 1999, 2001, 2002, 2003, 2004, 2005, 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 /* set a to abs(b) * signb: a=b when signb = SIGN(b), a=abs(b) when signb=1 */
  26 int
  27 mpfr_set4 (mpfr_ptr a, mpfr_srcptr b, mp_rnd_t rnd_mode, int signb)
  28 {
  29   /* Sign is ALWAYS copied */
  30   MPFR_SET_SIGN (a, signb);
  31
  32   /* Exponent is also always copied since if the number is singular,
  33      the exponent field determined the number.
  34      Can't use MPFR_SET_EXP since the exponent may be singular */
  35   MPFR_EXP (a) = MPFR_EXP (b);
  36
  37   if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (b)))
  38     {
  39       /* MPFR_SET_NAN, MPFR_SET_ZERO and MPFR_SET_INF are useless
  40          since MPFR_EXP (a) = MPFR_EXP (b) does the job */
  41       if (MPFR_IS_NAN (b))
  42         MPFR_RET_NAN;
  43       else
  44         MPFR_RET (0);
  45     }
  46   else if (MPFR_LIKELY (MPFR_PREC (b) == MPFR_PREC (a)))
  47     {
  48       /* Same precision and b is not singular:
  49        * just copy the mantissa, and set the exponent and the sign
  50        * The result is exact. */
  51       MPN_COPY (MPFR_MANT (a), MPFR_MANT (b),
  52                 (MPFR_PREC (b) + BITS_PER_MP_LIMB-1)/BITS_PER_MP_LIMB);
  53       MPFR_RET (0);
  54     }
  55   else
  56     {
  57       int inex;
  58
  59       /* Else Round B inside a */
  60       MPFR_RNDRAW (inex, a, MPFR_MANT (b), MPFR_PREC (b), rnd_mode, signb,
  61                    if (MPFR_UNLIKELY ( ++MPFR_EXP (a) > __gmpfr_emax))
  62                     return mpfr_overflow (a, rnd_mode, signb) );
  63       MPFR_RET (inex);
  64     }
  65 }
  66
  67 /* Set a to b  */
  68 #undef mpfr_set
  69 int
  70 mpfr_set (mpfr_ptr a, mpfr_srcptr b, mp_rnd_t rnd_mode)
  71 {
  72   return mpfr_set4 (a, b, rnd_mode, MPFR_SIGN (b));
  73 }
  74
  75 /* Set a to |b| */
  76 #undef mpfr_abs
  77 int
  78 mpfr_abs (mpfr_ptr a, mpfr_srcptr b, mp_rnd_t rnd_mode)
  79 {
  80   return mpfr_set4 (a, b, rnd_mode, MPFR_SIGN_POS);
  81 }