xref: /PHP-5.4/ext/bcmath/libbcmath/src/sub.c (revision c476bce2)
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