projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| 82492b51 KB |
1 | /*- |
| 2 | * Copyright (c) 1980 The Regents of the University of California. | |
| 3 | * All rights reserved. | |
| ce9c54b8 | 4 | * |
| ad787160 C |
5 | * This module is believed to contain source code proprietary to AT&T. |
| 6 | * Use and redistribution is subject to the Berkeley Software License | |
| 7 | * Agreement and your Software Agreement with AT&T (Western Electric). | |
| ee035c83 DW |
8 | */ |
| 9 | ||
| 82492b51 | 10 | #ifndef lint |
| ad787160 | 11 | static char sccsid[] = "@(#)pow_ii.c 5.4 (Berkeley) 4/12/91"; |
| 82492b51 KB |
12 | #endif /* not lint */ |
| 13 | ||
| 14 | /* Corrections by Robert P. Corbett, 1983 March 2 | |
| 15 | * Revised to restore portability, 1983 March 4 | |
| 16 | */ | |
| ce9c54b8 | 17 | |
| ee035c83 DW |
18 | long int pow_ii(ap, bp) |
| 19 | long int *ap, *bp; | |
| 20 | { | |
| ce9c54b8 | 21 | long int pow, x, n; |
| ce9c54b8 DW |
22 | |
| 23 | pow = 1; | |
| 24 | x = *ap; | |
| 25 | n = *bp; | |
| 26 | ||
| 27 | if (n == 0) | |
| 28 | return ( 1L ); | |
| 29 | ||
| 30 | if (x == 0) | |
| 2129c98e JB |
31 | { |
| 32 | if( n > 0 ) | |
| 33 | return ( 0L ); | |
| 34 | else | |
| 35 | return ( 1/x ); | |
| 36 | } | |
| ee035c83 | 37 | |
| ce9c54b8 DW |
38 | if (x == 1) |
| 39 | return ( 1L ); | |
| ee035c83 | 40 | |
| ce9c54b8 DW |
41 | if (x == -1) |
| 42 | { | |
| 43 | if (n < 0) | |
| ee035c83 | 44 | { |
| ce9c54b8 DW |
45 | if (n < -2) |
| 46 | n += 2; | |
| 47 | n = -n; | |
| 48 | } | |
| 49 | if (n % 2 == 0) | |
| 50 | return ( 1L ); | |
| ee035c83 | 51 | else |
| ce9c54b8 DW |
52 | return ( -1L ); |
| 53 | } | |
| 54 | ||
| 55 | if (n > 0) | |
| 56 | for( ; ; ) | |
| 57 | { | |
| 58 | if(n & 01) | |
| 59 | pow *= x; | |
| 60 | if(n >>= 1) | |
| 61 | x *= x; | |
| 62 | else | |
| 63 | break; | |
| ee035c83 | 64 | } |
| ce9c54b8 DW |
65 | else |
| 66 | pow = 0; | |
| 67 | ||
| 68 | return(pow); | |
| ee035c83 | 69 | } |