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