gcc/mpfr/cmp.c

/* mpfr_cmp -- compare two floating-point numbers

Copyright 1999, 2001, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
Contributed by the Arenaire and Cacao projects, INRIA.

This file is part of the GNU MPFR Library.

The GNU MPFR Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or (at your
option) any later version.

The GNU MPFR Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
License for more details.

You should have received a copy of the GNU Lesser General Public License
along with the GNU MPFR Library; see the file COPYING.LIB.  If not, write to
the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
MA 02110-1301, USA. */

#include "mpfr-impl.h"

/* returns 0 iff b = sign(s) * c
           a positive value iff b > sign(s) * c
           a negative value iff b < sign(s) * c
   returns 0 and sets erange flag if b and/or c is NaN.
*/

int
mpfr_cmp3 (mpfr_srcptr b, mpfr_srcptr c, int s)
{
  mp_exp_t be, ce;
  mp_size_t bn, cn;
  mp_limb_t *bp, *cp;

  s = MPFR_MULT_SIGN( s , MPFR_SIGN(c) );

  if (MPFR_ARE_SINGULAR(b, c))
    {
      if (MPFR_IS_NAN (b) || MPFR_IS_NAN (c))
        {
          MPFR_SET_ERANGE ();
          return 0;
        }
      else if (MPFR_IS_INF(b))
        {
          if (MPFR_IS_INF(c) && s == MPFR_SIGN(b) )
            return 0;
          else
            return MPFR_SIGN(b);
        }
      else if (MPFR_IS_INF(c))
        return -s;
      else if (MPFR_IS_ZERO(b))
        return MPFR_IS_ZERO(c) ? 0 : -s;
      else /* necessarily c=0 */
        return MPFR_SIGN(b);
    }
  /* b and c are real numbers */
  if (s != MPFR_SIGN(b))
    return MPFR_SIGN(b);

  /* now signs are equal */

  be = MPFR_GET_EXP (b);
  ce = MPFR_GET_EXP (c);
  if (be > ce)
    return s;
  if (be < ce)
    return -s;

  /* both signs and exponents are equal */

  bn = (MPFR_PREC(b)-1)/BITS_PER_MP_LIMB;
  cn = (MPFR_PREC(c)-1)/BITS_PER_MP_LIMB;

  bp = MPFR_MANT(b);
  cp = MPFR_MANT(c);

  for ( ; bn >= 0 && cn >= 0; bn--, cn--)
    {
      if (bp[bn] > cp[cn])
        return s;
      if (bp[bn] < cp[cn])
        return -s;
    }
  for ( ; bn >= 0; bn--)
    if (bp[bn])
      return s;
  for ( ; cn >= 0; cn--)
    if (cp[cn])
      return -s;

   return 0;
}

#undef mpfr_cmp
int
mpfr_cmp (mpfr_srcptr b, mpfr_srcptr c)
{
  return mpfr_cmp3 (b, c, 1);
}