/* mpfr_isinteger -- test if a mpfr variable is integer

Copyright 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 "gmp.h"
#include "gmp-impl.h"
#include "mpfr.h"
#include "mpfr-impl.h"

int 
mpfr_isinteger (mpfr_srcptr x)
{
  mp_exp_t expo;
  mp_prec_t prec;
  mp_size_t xn;
  mp_limb_t *xp;

  if (!MPFR_IS_FP(x))
    return 0;

  if (MPFR_IS_ZERO(x))
    return 1;

  expo = MPFR_EXP(x);
  if (expo <= 0)
    return 0;

  prec = MPFR_PREC(x);
  if (expo >= prec)
    return 1;

  /* 0 < expo < prec */

  xn = (prec - 1) / BITS_PER_MP_LIMB;  /* index of last limb */
  xn -= (mp_size_t) (expo / BITS_PER_MP_LIMB);
  /* now the index of the last limb containing bits of the fractional part */

  xp = MPFR_MANT(x);
  MPFR_ASSERTN(xn >= 0);
  if (xp[xn] << (expo % BITS_PER_MP_LIMB) != 0)
    return 0;
  while (--xn >= 0)
    if (xp[xn] != 0)
      return 0;
  return 1;
}