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/* sub.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"
/* Here is the full subtract routine that takes care of negative numbers.
N2 is subtracted from N1 and the result placed in RESULT. SCALE_MIN
is the minimum scale for the result. */
void
bc_sub (n1, n2, result, scale_min)
bc_num n1, n2, *result;
int scale_min;
{
bc_num diff = NULL;
int cmp_res;
int res_scale;
if (n1->n_sign != n2->n_sign)
{
diff = _bc_do_add (n1, n2, scale_min);
diff->n_sign = n1->n_sign;
}
else
{
/* subtraction must be done. */
/* Compare magnitudes. */
cmp_res = _bc_do_compare (n1, n2, FALSE, FALSE);
switch (cmp_res)
{
case -1:
/* n1 is less than n2, subtract n1 from n2. */
diff = _bc_do_sub (n2, n1, scale_min);
diff->n_sign = (n2->n_sign == PLUS ? MINUS : PLUS);
break;
case 0:
/* They are equal! return zero! */
res_scale = MAX (scale_min, MAX(n1->n_scale, n2->n_scale));
diff = bc_new_num (1, res_scale);
memset (diff->n_value, 0, res_scale+1);
break;
case 1:
/* n2 is less than n1, subtract n2 from n1. */
diff = _bc_do_sub (n1, n2, scale_min);
diff->n_sign = n1->n_sign;
break;
}
}
/* Clean up and return. */
bc_free_num (result);
*result = diff;
}
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