xref: /PHP-5.6/ext/bcmath/libbcmath/src/raise.c (revision f200f739)
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
bc_raise(bc_num num1,bc_num num2,bc_num * result,int scale TSRMLS_DC)47 bc_raise (bc_num num1, bc_num num2, bc_num *result, int scale TSRMLS_DC)
48 {
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    if (num2->n_scale != 0)
58      bc_rt_warn ("non-zero scale in exponent");
59    exponent = bc_num2long (num2);
60    if (exponent == 0 && (num2->n_len > 1 || num2->n_value[0] != 0))
61        bc_rt_error ("exponent too large in raise");
62 
63    /* Special case if exponent is a zero. */
64    if (exponent == 0)
65      {
66        bc_free_num (result);
67        *result = bc_copy_num (BCG(_one_));
68        return;
69      }
70 
71    /* Other initializations. */
72    if (exponent < 0)
73      {
74        neg = TRUE;
75        exponent = -exponent;
76        rscale = scale;
77      }
78    else
79      {
80        neg = FALSE;
81        rscale = MIN (num1->n_scale*exponent, MAX(scale, num1->n_scale));
82      }
83 
84    /* Set initial value of temp.  */
85    power = bc_copy_num (num1);
86    pwrscale = num1->n_scale;
87    while ((exponent & 1) == 0)
88      {
89        pwrscale = 2*pwrscale;
90        bc_multiply (power, power, &power, pwrscale TSRMLS_CC);
91        exponent = exponent >> 1;
92      }
93    temp = bc_copy_num (power);
94    calcscale = pwrscale;
95    exponent = exponent >> 1;
96 
97    /* Do the calculation. */
98    while (exponent > 0)
99      {
100        pwrscale = 2*pwrscale;
101        bc_multiply (power, power, &power, pwrscale TSRMLS_CC);
102        if ((exponent & 1) == 1) {
103 	 calcscale = pwrscale + calcscale;
104 	 bc_multiply (temp, power, &temp, calcscale TSRMLS_CC);
105        }
106        exponent = exponent >> 1;
107      }
108 
109    /* Assign the value. */
110    if (neg)
111      {
112        bc_divide (BCG(_one_), temp, result, rscale TSRMLS_CC);
113        bc_free_num (&temp);
114      }
115    else
116      {
117        bc_free_num (result);
118        *result = temp;
119        if ((*result)->n_scale > rscale)
120 	 (*result)->n_scale = rscale;
121      }
122    bc_free_num (&power);
123 }
124 
125