| 1 | #include "complex" |
| 2 | |
| 3 | pow_zi(p, a, b) /* p = a**b */ |
| 4 | dcomplex *p, *a; |
| 5 | long int *b; |
| 6 | { |
| 7 | long int n; |
| 8 | double t; |
| 9 | dcomplex x; |
| 10 | |
| 11 | n = *b; |
| 12 | p->dreal = 1; |
| 13 | p->dimag = 0; |
| 14 | |
| 15 | if(n == 0) |
| 16 | return; |
| 17 | if(n < 0) |
| 18 | { |
| 19 | n = -n; |
| 20 | z_div(&x, a); |
| 21 | } |
| 22 | else |
| 23 | { |
| 24 | x.dreal = a->dreal; |
| 25 | x.dimag = a->dimag; |
| 26 | } |
| 27 | |
| 28 | for( ; ; ) |
| 29 | { |
| 30 | if(n & 01) |
| 31 | { |
| 32 | t = p->dreal * x.dreal - p->dimag * x.dimag; |
| 33 | p->dimag = p->dreal * x.dimag + p->dimag * x.dreal; |
| 34 | p->dreal = t; |
| 35 | } |
| 36 | if(n >>= 1) |
| 37 | { |
| 38 | t = x.dreal * x.dreal - x.dimag * x.dimag; |
| 39 | x.dimag = 2 * x.dreal * x.dimag; |
| 40 | x.dreal = t; |
| 41 | } |
| 42 | else |
| 43 | break; |
| 44 | } |
| 45 | } |