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Annotation of 43BSD/usr.lib/libF77/pow_zi.c, revision 1.1.1.1

1.1       root        1: /*
                      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.
                      5:  *
                      6:  *     @(#)pow_zi.c    5.1     6/7/85
                      7:  */
                      8: 
                      9: #include "complex"
                     10: 
                     11: pow_zi(p, a, b)        /* p = a**b  */
                     12: dcomplex *p, *a;
                     13: long int *b;
                     14: {
                     15: long int n;
                     16: double t;
                     17: dcomplex x;
                     18: 
                     19: n = *b;
                     20: p->dreal = 1;
                     21: p->dimag = 0;
                     22: 
                     23: if(n == 0)
                     24:        return;
                     25: if(n < 0)
                     26:        {
                     27:        n = -n;
                     28:        z_div(&x, p, a);
                     29:        }
                     30: else
                     31:        {
                     32:        x.dreal = a->dreal;
                     33:        x.dimag = a->dimag;
                     34:        }
                     35: 
                     36: for( ; ; )
                     37:        {
                     38:        if(n & 01)
                     39:                {
                     40:                t = p->dreal * x.dreal - p->dimag * x.dimag;
                     41:                p->dimag = p->dreal * x.dimag + p->dimag * x.dreal;
                     42:                p->dreal = t;
                     43:                }
                     44:        if(n >>= 1)
                     45:                {
                     46:                t = x.dreal * x.dreal - x.dimag * x.dimag;
                     47:                x.dimag = 2 * x.dreal * x.dimag;
                     48:                x.dreal = t;
                     49:                }
                     50:        else
                     51:                break;
                     52:        }
                     53: }

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