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

   1 /* mpfr_cmpabs -- compare the absolute values of two FP numbers
   2
   3 Copyright 1999, 2001-2004, 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 /* Return a positive value if abs(b) > abs(c), 0 if abs(b) = abs(c), and
  26    a negative value if abs(b) < abs(c). Neither b nor c may be NaN. */
  27
  28 int
  29 mpfr_cmpabs (mpfr_srcptr b, mpfr_srcptr c)
  30 {
  31   mpfr_exp_t be, ce;
  32   mp_size_t bn, cn;
  33   mp_limb_t *bp, *cp;
  34
  35   if (MPFR_ARE_SINGULAR (b, c))
  36     {
  37       if (MPFR_IS_NAN (b) || MPFR_IS_NAN (c))
  38         {
  39           MPFR_SET_ERANGE ();
  40           return 0;
  41         }
  42       else if (MPFR_IS_INF (b))
  43         return ! MPFR_IS_INF (c);
  44       else if (MPFR_IS_INF (c))
  45         return -1;
  46       else if (MPFR_IS_ZERO (c))
  47         return ! MPFR_IS_ZERO (b);
  48       else /* b == 0 */
  49         return -1;
  50     }
  51
  52   MPFR_ASSERTD (MPFR_IS_PURE_FP (b));
  53   MPFR_ASSERTD (MPFR_IS_PURE_FP (c));
  54
  55   /* Now that we know that b and c are pure FP numbers (i.e. they have
  56      a meaningful exponent), we use MPFR_EXP instead of MPFR_GET_EXP to
  57      allow exponents outside the current exponent range. For instance,
  58      this is useful for mpfr_pow, which compares values to __gmpfr_one.
  59      This is for internal use only! For compatibility with other MPFR
  60      versions, the user must still provide values that are representable
  61      in the current exponent range. */
  62   be = MPFR_EXP (b);
  63   ce = MPFR_EXP (c);
  64   if (be > ce)
  65     return 1;
  66   if (be < ce)
  67     return -1;
  68
  69   /* exponents are equal */
  70
  71   bn = MPFR_LIMB_SIZE(b)-1;
  72   cn = MPFR_LIMB_SIZE(c)-1;
  73
  74   bp = MPFR_MANT(b);
  75   cp = MPFR_MANT(c);
  76
  77   for ( ; bn >= 0 && cn >= 0; bn--, cn--)
  78     {
  79       if (bp[bn] > cp[cn])
  80         return 1;
  81       if (bp[bn] < cp[cn])
  82         return -1;
  83     }
  84
  85   for ( ; bn >= 0; bn--)
  86     if (bp[bn])
  87       return 1;
  88
  89   for ( ; cn >= 0; cn--)
  90     if (cp[cn])
  91       return -1;
  92
  93    return 0;
  94 }