BSD 4_3_Tahoe release

[unix-history] / usr / src / usr.lib / libF77 / pow_zi.c

/*
* Copyright (c) 1980 Regents of the University of California.
* All rights reserved.  The Berkeley software License Agreement
* specifies the terms and conditions for redistribution.
*
*      @(#)pow_zi.c    5.2     1/24/88
*/

#include "complex"

#define Z_MULEQ(A,B)    \
       t = (A).dreal * (B).dreal - (A).dimag * (B).dimag,\
       (A).dimag = (A).dreal * (B).dimag + (A).dimag * (B).dreal,\
       (A).dreal = t   /* A *= B */

void
pow_zi(p, a, b)         /* p = a**b  */
       dcomplex *p, *a;
       long int *b;
{
       register long n = *b;
       double t;
       dcomplex x;

       x = *a;
       p->dreal = (double)1, p->dimag = (double)0;
       if (!n)
               return;
       if (n < 0) {
               z_div(&x, p, a);
               n = -n;
       }
       while (!(n&1)) {
               Z_MULEQ(x, x);
               n >>= 1;
       }
       for (*p = x; --n > 0; Z_MULEQ(*p, x))
               while (!(n&1)) {
                       Z_MULEQ(x, x);
                       n >>= 1;
               }
}