1
2/*
3 *  M_APM  -  mapmipwr.c
4 *
5 *  Copyright (C) 1999 - 2007   Michael C. Ring
6 *
7 *  Permission to use, copy, and distribute this software and its
8 *  documentation for any purpose with or without fee is hereby granted,
9 *  provided that the above copyright notice appear in all copies and
10 *  that both that copyright notice and this permission notice appear
11 *  in supporting documentation.
12 *
13 *  Permission to modify the software is granted. Permission to distribute
14 *  the modified code is granted. Modifications are to be distributed by
15 *  using the file 'license.txt' as a template to modify the file header.
16 *  'license.txt' is available in the official MAPM distribution.
17 *
18 *  This software is provided "as is" without express or implied warranty.
19 */
20
21/*
22 *      $Id: mapmipwr.c,v 1.6 2007/12/03 01:54:39 mike Exp $
23 *
24 *      This file contains the Integer Power function.
25 *
26 *      $Log: mapmipwr.c,v $
27 *      Revision 1.6  2007/12/03 01:54:39  mike
28 *      Update license
29 *
30 *      Revision 1.5  2002/11/03 21:10:32  mike
31 *      Updated function parameters to use the modern style
32 *
33 *      Revision 1.4  2000/09/23 19:46:04  mike
34 *      change divide call to reciprocal
35 *
36 *      Revision 1.3  2000/05/24 17:03:35  mike
37 *      return 1 when input is 0^0
38 *
39 *      Revision 1.2  1999/09/18 01:34:35  mike
40 *      minor tweaks
41 *
42 *      Revision 1.1  1999/09/18 01:33:09  mike
43 *      Initial revision
44 */
45
46#include "m_apm_lc.h"
47
48/****************************************************************************/
49void	m_apm_integer_pow(M_APM rr, int places, M_APM aa, int mexp)
50{
51M_APM   tmp0, tmpy, tmpz;
52int	nexp, ii, signflag, local_precision;
53
54if (mexp == 0)
55  {
56   m_apm_copy(rr, MM_One);
57   return;
58  }
59else
60  {
61   if (mexp > 0)
62     {
63      signflag = 0;
64      nexp     = mexp;
65     }
66   else
67     {
68      signflag = 1;
69      nexp     = -mexp;
70     }
71  }
72
73if (aa->m_apm_sign == 0)
74  {
75   M_set_to_zero(rr);
76   return;
77  }
78
79tmp0 = M_get_stack_var();
80tmpy = M_get_stack_var();
81tmpz = M_get_stack_var();
82
83local_precision = places + 8;
84
85m_apm_copy(tmpy, MM_One);
86m_apm_copy(tmpz, aa);
87
88while (TRUE)
89  {
90   ii   = nexp & 1;
91   nexp = nexp >> 1;
92
93   if (ii != 0)                       /* exponent -was- odd */
94     {
95      m_apm_multiply(tmp0, tmpy, tmpz);
96      m_apm_round(tmpy, local_precision, tmp0);
97
98      if (nexp == 0)
99        break;
100     }
101
102   m_apm_multiply(tmp0, tmpz, tmpz);
103   m_apm_round(tmpz, local_precision, tmp0);
104  }
105
106if (signflag)
107  {
108   m_apm_reciprocal(rr, places, tmpy);
109  }
110else
111  {
112   m_apm_round(rr, places, tmpy);
113  }
114
115M_restore_stack(3);
116}
117/****************************************************************************/
118