1 /* sub.c: bcmath library file. */
2 /*
3 Copyright (C) 1991, 1992, 1993, 1994, 1997 Free Software Foundation, Inc.
4 Copyright (C) 2000 Philip A. Nelson
5
6 This library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2 of the License, or (at your option) any later version.
10
11 This library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details. (COPYING.LIB)
15
16 You should have received a copy of the GNU Lesser General Public
17 License along with this library; if not, write to:
18
19 The Free Software Foundation, Inc.
20 59 Temple Place, Suite 330
21 Boston, MA 02111-1307 USA.
22
23 You may contact the author by:
24 e-mail: philnelson@acm.org
25 us-mail: Philip A. Nelson
26 Computer Science Department, 9062
27 Western Washington University
28 Bellingham, WA 98226-9062
29
30 *************************************************************************/
31
32 #include <config.h>
33 #include <stdio.h>
34 #include <assert.h>
35 #include <stdlib.h>
36 #include <ctype.h>
37 #include <stdarg.h>
38 #include "bcmath.h"
39 #include "private.h"
40
41
42 /* Here is the full subtract routine that takes care of negative numbers.
43 N2 is subtracted from N1 and the result placed in RESULT. SCALE_MIN
44 is the minimum scale for the result. */
45
46 void
bc_sub(n1,n2,result,scale_min)47 bc_sub (n1, n2, result, scale_min)
48 bc_num n1, n2, *result;
49 int scale_min;
50 {
51 bc_num diff = NULL;
52 int cmp_res;
53 int res_scale;
54
55 if (n1->n_sign != n2->n_sign)
56 {
57 diff = _bc_do_add (n1, n2, scale_min);
58 diff->n_sign = n1->n_sign;
59 }
60 else
61 {
62 /* subtraction must be done. */
63 /* Compare magnitudes. */
64 cmp_res = _bc_do_compare (n1, n2, FALSE, FALSE);
65 switch (cmp_res)
66 {
67 case -1:
68 /* n1 is less than n2, subtract n1 from n2. */
69 diff = _bc_do_sub (n2, n1, scale_min);
70 diff->n_sign = (n2->n_sign == PLUS ? MINUS : PLUS);
71 break;
72 case 0:
73 /* They are equal! return zero! */
74 res_scale = MAX (scale_min, MAX(n1->n_scale, n2->n_scale));
75 diff = bc_new_num (1, res_scale);
76 memset (diff->n_value, 0, res_scale+1);
77 break;
78 case 1:
79 /* n2 is less than n1, subtract n2 from n1. */
80 diff = _bc_do_sub (n1, n2, scale_min);
81 diff->n_sign = n1->n_sign;
82 break;
83 }
84 }
85
86 /* Clean up and return. */
87 bc_free_num (result);
88 *result = diff;
89 }
90
91
