Artifact Content
Not logged in

Artifact 182452eabdfec4320ce8fb0925fa3505fdc3777e:


/* mpfr_cmp_ui -- compare a floating-point number with a machine integer

Copyright 1999, 2001, 2002 Free Software Foundation, Inc.

This file is part of the MPFR Library.

The 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 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 MPFR Library; see the file COPYING.LIB.  If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA. */

#include <stdio.h>
#include "gmp.h"
#include "gmp-impl.h"
#include "longlong.h"
#include "mpfr.h"
#include "mpfr-impl.h"

/* returns a positive value if b>i*2^f,
           a negative value if b<i*2^f,
           zero if b=i*2^f
*/

int 
mpfr_cmp_ui_2exp (mpfr_srcptr b, unsigned long int i, int f)
{
  int e, k, bn;
  mp_limb_t c, *bp;

  MPFR_ASSERTN(!MPFR_IS_NAN(b));

  if (MPFR_IS_INF(b))
    return MPFR_SIGN(b);

  /* now b is neither NaN nor +/-Infinity */
  if (MPFR_IS_ZERO(b))
    return i ? -1 : 0;
  else if (MPFR_SIGN(b) < 0)
    return -1;
  /* now b>0 */
  else if (i == 0)
    return 1;
  else
    { /* b>0, i>0 */
      e = MPFR_EXP(b); /* 2^(e-1) <= b < 2^e */
      if (e > f + BITS_PER_MP_LIMB)
        return 1;

    c = (mp_limb_t) i;
    count_leading_zeros(k, c);
    k = f + BITS_PER_MP_LIMB - k; /* 2^(k-1) <= i*2^f < 2^k */
    if (k != e)
      return e - k;

    /* now k=e */
    c <<= f + BITS_PER_MP_LIMB - k;
    bn = (MPFR_PREC(b) - 1) / BITS_PER_MP_LIMB;
    bp = MPFR_MANT(b) + bn;
    if (*bp > c)
      return 1;
    if (*bp < c)
      return -1;

    /* most significant limbs agree, check remaining limbs from b */
    while (--bn >= 0)
      if (*--bp)
        return 1;
    return 0;
    }
}

/* returns a positive value if b>i*2^f,
           a negative value if b<i*2^f,
           zero if b=i*2^f 
*/

int 
mpfr_cmp_si_2exp (mpfr_srcptr b, long int i, int f)
{
  int e, k, bn, si;
  mp_limb_t c, *bp;

  MPFR_ASSERTN(!MPFR_IS_NAN(b));

  si = i < 0 ? -1 : 1; /* sign of i */
  if (MPFR_IS_INF(b) || (MPFR_NOTZERO(b) && MPFR_SIGN(b) != si))
    return MPFR_SIGN(b);
  /* both signs differ */
  else if (MPFR_IS_ZERO(b) || i == 0)
    return i == 0 ? (MPFR_IS_ZERO(b) ? 0 : MPFR_SIGN(b)) : -si;
  else
    { /* b and i are of same sign */
      e = MPFR_EXP(b); /* 2^(e-1) <= b < 2^e */
      if (e > f + BITS_PER_MP_LIMB)
        return si;

      c = i < 0 ? - (mp_limb_t) i : (mp_limb_t) i;
      count_leading_zeros(k, c);
      k = f + BITS_PER_MP_LIMB - k; /* 2^(k-1) <= i*2^f < 2^k */
      if (k != e)
        return si * (e - k);

      /* now k = e */
      c <<= f + BITS_PER_MP_LIMB - k;
      bn = (MPFR_PREC(b) - 1) / BITS_PER_MP_LIMB;
      bp = MPFR_MANT(b) + bn;
      if (*bp > c)
        return si;
      if (*bp < c)
        return -si;

      /* most significant limbs agree, check remaining limbs from b */
      while (--bn >= 0)
        if (*--bp)
          return si;
      return 0;
    }
}