******** fig3.22 **********

	void
	add_polynomial( POLYNOMIAL poly1, POLYNOMIAL poly2, POLYNOMIAL poly_sum )
	{
		int i;

		zero_polynomial( poly_sum );
		poly_sum->high_power = max( poly1->high_power, poly2->high_power );

		for(i=poly_sum->high_power; i>=0; i-- )
			poly_sum->coeff_array[i] = poly1->coeff_array[i] + poly2->coeff_array[i];
	}