compare.c

/* compare.c: bcmath library file. */
/*
    Copyright (C) 1991, 1992, 1993, 1994, 1997 Free Software Foundation, Inc.
    Copyright (C) 2000 Philip A. Nelson

    This 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 of the License, or (at your option) any later version.

    This 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.  (COPYING.LIB)

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to:

      The Free Software Foundation, Inc.
      59 Temple Place, Suite 330
      Boston, MA 02111-1307 USA.

    You may contact the author by:
       e-mail:  philnelson@acm.org
      us-mail:  Philip A. Nelson
                Computer Science Department, 9062
                Western Washington University
                Bellingham, WA 98226-9062

*************************************************************************/

#include <config.h>
#include <stdio.h>
#include <assert.h>
#include <stdlib.h>
#include <ctype.h>
#include <stdarg.h>
#include "bcmath.h"
#include "private.h"


/* Compare two bc numbers.  Return value is 0 if equal, -1 if N1 is less
   than N2 and +1 if N1 is greater than N2.  If USE_SIGN is false, just
   compare the magnitudes. */

 int
_bc_do_compare (n1, n2, use_sign, ignore_last)
     bc_num n1, n2;
     int use_sign;
     int ignore_last;
{
  char *n1ptr, *n2ptr;
  int  count;

  /* First, compare signs. */
  if (use_sign && n1->n_sign != n2->n_sign)
    {
      if (n1->n_sign == PLUS)
	return (1);	/* Positive N1 > Negative N2 */
      else
	return (-1);	/* Negative N1 < Positive N1 */
    }

  /* Now compare the magnitude. */
  if (n1->n_len != n2->n_len)
    {
      if (n1->n_len > n2->n_len)
	{
	  /* Magnitude of n1 > n2. */
	  if (!use_sign || n1->n_sign == PLUS)
	    return (1);
	  else
	    return (-1);
	}
      else
	{
	  /* Magnitude of n1 < n2. */
	  if (!use_sign || n1->n_sign == PLUS)
	    return (-1);
	  else
	    return (1);
	}
    }

  /* If we get here, they have the same number of integer digits.
     check the integer part and the equal length part of the fraction. */
  count = n1->n_len + MIN (n1->n_scale, n2->n_scale);
  n1ptr = n1->n_value;
  n2ptr = n2->n_value;

  while ((count > 0) && (*n1ptr == *n2ptr))
    {
      n1ptr++;
      n2ptr++;
      count--;
    }
  if (ignore_last && count == 1 && n1->n_scale == n2->n_scale)
    return (0);
  if (count != 0)
    {
      if (*n1ptr > *n2ptr)
	{
	  /* Magnitude of n1 > n2. */
	  if (!use_sign || n1->n_sign == PLUS)
	    return (1);
	  else
	    return (-1);
	}
      else
	{
	  /* Magnitude of n1 < n2. */
	  if (!use_sign || n1->n_sign == PLUS)
	    return (-1);
	  else
	    return (1);
	}
    }

  /* They are equal up to the last part of the equal part of the fraction. */
  if (n1->n_scale != n2->n_scale)
    {
      if (n1->n_scale > n2->n_scale)
	{
	  for (count = n1->n_scale-n2->n_scale; count>0; count--)
	    if (*n1ptr++ != 0)
	      {
		/* Magnitude of n1 > n2. */
		if (!use_sign || n1->n_sign == PLUS)
		  return (1);
		else
		  return (-1);
	      }
	}
      else
	{
	  for (count = n2->n_scale-n1->n_scale; count>0; count--)
	    if (*n2ptr++ != 0)
	      {
		/* Magnitude of n1 < n2. */
		if (!use_sign || n1->n_sign == PLUS)
		  return (-1);
		else
		  return (1);
	      }
	}
    }

  /* They must be equal! */
  return (0);
}


/* This is the "user callable" routine to compare numbers N1 and N2. */

int
bc_compare (n1, n2)
     bc_num n1, n2;
{
  return _bc_do_compare (n1, n2, TRUE, FALSE);
}