projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| ee035c83 | 1 | /* |
| a7868ad7 RE |
2 | * Copyright (c) 1980 Regents of the University of California. |
| 3 | * All rights reserved. The Berkeley software License Agreement | |
| 4 | * specifies the terms and conditions for redistribution. | |
| ce9c54b8 | 5 | * |
| 2129c98e | 6 | * @(#)pow_ii.c 5.3 %G% |
| bb3ec388 | 7 | * |
| ce9c54b8 DW |
8 | * Corrections by Robert P. Corbett, 1983 March 2 |
| 9 | * Revised to restore portability, 1983 March 4 | |
| ee035c83 DW |
10 | */ |
| 11 | ||
| ce9c54b8 | 12 | |
| ee035c83 DW |
13 | long int pow_ii(ap, bp) |
| 14 | long int *ap, *bp; | |
| 15 | { | |
| ce9c54b8 | 16 | long int pow, x, n; |
| ce9c54b8 DW |
17 | |
| 18 | pow = 1; | |
| 19 | x = *ap; | |
| 20 | n = *bp; | |
| 21 | ||
| 22 | if (n == 0) | |
| 23 | return ( 1L ); | |
| 24 | ||
| 25 | if (x == 0) | |
| 2129c98e JB |
26 | { |
| 27 | if( n > 0 ) | |
| 28 | return ( 0L ); | |
| 29 | else | |
| 30 | return ( 1/x ); | |
| 31 | } | |
| ee035c83 | 32 | |
| ce9c54b8 DW |
33 | if (x == 1) |
| 34 | return ( 1L ); | |
| ee035c83 | 35 | |
| ce9c54b8 DW |
36 | if (x == -1) |
| 37 | { | |
| 38 | if (n < 0) | |
| ee035c83 | 39 | { |
| ce9c54b8 DW |
40 | if (n < -2) |
| 41 | n += 2; | |
| 42 | n = -n; | |
| 43 | } | |
| 44 | if (n % 2 == 0) | |
| 45 | return ( 1L ); | |
| ee035c83 | 46 | else |
| ce9c54b8 DW |
47 | return ( -1L ); |
| 48 | } | |
| 49 | ||
| 50 | if (n > 0) | |
| 51 | for( ; ; ) | |
| 52 | { | |
| 53 | if(n & 01) | |
| 54 | pow *= x; | |
| 55 | if(n >>= 1) | |
| 56 | x *= x; | |
| 57 | else | |
| 58 | break; | |
| ee035c83 | 59 | } |
| ce9c54b8 DW |
60 | else |
| 61 | pow = 0; | |
| 62 | ||
| 63 | return(pow); | |
| ee035c83 | 64 | } |