1 : /* raise.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 : /* Raise NUM1 to the NUM2 power. The result is placed in RESULT.
43 : Maximum exponent is LONG_MAX. If a NUM2 is not an integer,
44 : only the integer part is used. */
45 :
46 : void
47 : bc_raise (bc_num num1, bc_num num2, bc_num *result, int scale TSRMLS_DC)
48 5 : {
49 : bc_num temp, power;
50 : long exponent;
51 : int rscale;
52 : int pwrscale;
53 : int calcscale;
54 : char neg;
55 :
56 : /* Check the exponent for scale digits and convert to a long. */
57 5 : if (num2->n_scale != 0)
58 0 : bc_rt_warn ("non-zero scale in exponent");
59 5 : exponent = bc_num2long (num2);
60 5 : if (exponent == 0 && (num2->n_len > 1 || num2->n_value[0] != 0))
61 0 : bc_rt_error ("exponent too large in raise");
62 :
63 : /* Special case if exponent is a zero. */
64 5 : if (exponent == 0)
65 : {
66 1 : bc_free_num (result);
67 1 : *result = bc_copy_num (BCG(_one_));
68 1 : return;
69 : }
70 :
71 : /* Other initializations. */
72 4 : if (exponent < 0)
73 : {
74 0 : neg = TRUE;
75 0 : exponent = -exponent;
76 0 : rscale = scale;
77 : }
78 : else
79 : {
80 4 : neg = FALSE;
81 4 : rscale = MIN (num1->n_scale*exponent, MAX(scale, num1->n_scale));
82 : }
83 :
84 : /* Set initial value of temp. */
85 4 : power = bc_copy_num (num1);
86 4 : pwrscale = num1->n_scale;
87 15 : while ((exponent & 1) == 0)
88 : {
89 7 : pwrscale = 2*pwrscale;
90 7 : bc_multiply (power, power, &power, pwrscale TSRMLS_CC);
91 7 : exponent = exponent >> 1;
92 : }
93 4 : temp = bc_copy_num (power);
94 4 : calcscale = pwrscale;
95 4 : exponent = exponent >> 1;
96 :
97 : /* Do the calculation. */
98 13 : while (exponent > 0)
99 : {
100 5 : pwrscale = 2*pwrscale;
101 5 : bc_multiply (power, power, &power, pwrscale TSRMLS_CC);
102 5 : if ((exponent & 1) == 1) {
103 3 : calcscale = pwrscale + calcscale;
104 3 : bc_multiply (temp, power, &temp, calcscale TSRMLS_CC);
105 : }
106 5 : exponent = exponent >> 1;
107 : }
108 :
109 : /* Assign the value. */
110 4 : if (neg)
111 : {
112 0 : bc_divide (BCG(_one_), temp, result, rscale TSRMLS_CC);
113 0 : bc_free_num (&temp);
114 : }
115 : else
116 : {
117 4 : bc_free_num (result);
118 4 : *result = temp;
119 4 : if ((*result)->n_scale > rscale)
120 0 : (*result)->n_scale = rscale;
121 : }
122 4 : bc_free_num (&power);
123 : }
124 :
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