gcc/libf2c/libF77/pow_zi.c

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#include "f2c.h"
extern void z_div (doublecomplex *, doublecomplex *, doublecomplex *);
void
pow_zi (doublecomplex * p, doublecomplex * a, integer * b) /* p = a**b */
{
integer n;
unsigned long u;
double t;
doublecomplex q, x;
static doublecomplex one = { 1.0, 0.0 };
n = *b;
q.r = 1;
q.i = 0;
if (n == 0)
goto done;
if (n < 0)
{
n = -n;
z_div (&x, &one, a);
}
else
{
x.r = a->r;
x.i = a->i;
}
for (u = n;;)
{
if (u & 01)
{
t = q.r * x.r - q.i * x.i;
q.i = q.r * x.i + q.i * x.r;
q.r = t;
}
if (u >>= 1)
{
t = x.r * x.r - x.i * x.i;
x.i = 2 * x.r * x.i;
x.r = t;
}
else
break;
}
done:
p->i = q.i;
p->r = q.r;
}