r->r = r->i = 0.;
res.r = res.i = 0.;
void z_sqrt(doublecomplex *r, doublecomplex *z)#endif{double mag;if( (mag = f__cabs(z->r, z->i)) == 0.)	r->r = r->i = 0.;else if(z->r > 0)	{	r->r = sqrt(0.5 * (mag + z->r) );	r->i = z->i / r->r / 2;	}else	{	r->i = sqrt(0.5 * (mag - z->r) );	if(z->i < 0)		r->i = - r->i;	r->r = z->i / r->i / 2;	}}