contrib/mpfr/cmp.c

   1 /* mpfr_cmp -- compare two floating-point numbers
   2
   3 Copyright 1999, 2001, 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 /* returns 0 iff b = sign(s) * c
  26            a positive value iff b > sign(s) * c
  27            a negative value iff b < sign(s) * c
  28    returns 0 and sets erange flag if b and/or c is NaN.
  29 */
  30
  31 int
  32 mpfr_cmp3 (mpfr_srcptr b, mpfr_srcptr c, int s)
  33 {
  34   mp_exp_t be, ce;
  35   mp_size_t bn, cn;
  36   mp_limb_t *bp, *cp;
  37
  38   s = MPFR_MULT_SIGN( s , MPFR_SIGN(c) );
  39
  40   if (MPFR_ARE_SINGULAR(b, c))
  41     {
  42       if (MPFR_IS_NAN (b) || MPFR_IS_NAN (c))
  43         {
  44           MPFR_SET_ERANGE ();
  45           return 0;
  46         }
  47       else if (MPFR_IS_INF(b))
  48         {
  49           if (MPFR_IS_INF(c) && s == MPFR_SIGN(b) )
  50             return 0;
  51           else
  52             return MPFR_SIGN(b);
  53         }
  54       else if (MPFR_IS_INF(c))
  55         return -s;
  56       else if (MPFR_IS_ZERO(b))
  57         return MPFR_IS_ZERO(c) ? 0 : -s;
  58       else /* necessarily c=0 */
  59         return MPFR_SIGN(b);
  60     }
  61   /* b and c are real numbers */
  62   if (s != MPFR_SIGN(b))
  63     return MPFR_SIGN(b);
  64
  65   /* now signs are equal */
  66
  67   be = MPFR_GET_EXP (b);
  68   ce = MPFR_GET_EXP (c);
  69   if (be > ce)
  70     return s;
  71   if (be < ce)
  72     return -s;
  73
  74   /* both signs and exponents are equal */
  75
  76   bn = (MPFR_PREC(b)-1)/BITS_PER_MP_LIMB;
  77   cn = (MPFR_PREC(c)-1)/BITS_PER_MP_LIMB;
  78
  79   bp = MPFR_MANT(b);
  80   cp = MPFR_MANT(c);
  81
  82   for ( ; bn >= 0 && cn >= 0; bn--, cn--)
  83     {
  84       if (bp[bn] > cp[cn])
  85         return s;
  86       if (bp[bn] < cp[cn])
  87         return -s;
  88     }
  89   for ( ; bn >= 0; bn--)
  90     if (bp[bn])
  91       return s;
  92   for ( ; cn >= 0; cn--)
  93     if (cp[cn])
  94       return -s;
  95
  96    return 0;
  97 }
  98
  99 #undef mpfr_cmp
 100 int
 101 mpfr_cmp (mpfr_srcptr b, mpfr_srcptr c)
 102 {
 103   return mpfr_cmp3 (b, c, 1);
 104 }