/**
 * Demonstrates the differences in scope and lifetime of variables.
 * 
 * @author Pete Nordquist
 * @version 061019
 */
public class W04N03
{
	// 'global' scope -- visible to all methods
	// these example variables are used for error checking in the methods below
	private static final double MAXINPUT = 5;
	private static final double MAXRESULT = 200.0;
	
	public static void main(String[] args)
	{

		// d1 and d2 have local scope
		// visible from the point they are defined to the closing brace
		// that ends the block in which they were defined.
		double d1 = IO.readDouble("1st Num? ");
		// turn d1 non-negative
		d1 = Math.abs(d1);
		
		// if d1 is too big
		if (d1 > MAXINPUT)
			// print an error
			System.err.println("d1, " + d1 + ", is too big." +
				"  Max allowable is " + MAXINPUT);
		
		else
		{
			// read d2
			double d2 = IO.readDouble("2nd Num? ");
			// turn d2 positive
			d2 = Math.abs(d2);
			
			// if d2 is too big
			if (d2 > MAXINPUT)
				// print an error
				System.err.println("d2, " + d2 + ", is too big." +
					"  Max allowable is " + MAXINPUT);
			else
			{
				// calculate result
				double result = calculatePowers(d1, d2);
				if (result != 0)
					System.out.println("result is " + result);
			}
		}
	}
	
	/**
	 * x and y have 'parameter' scope -- they are visible in calculatePowers()
	 * but not in main()
	 * calculatePowers checks its result and prints an error if it is too big
	 *    and returns 0 in this case
	 * @return the value x raised to the y power.
	 */
	public static double calculatePowers(double x, double y)
	{
		// result has 'local' scope
		double result;
		// call the pow method in the Math class
		result = Math.pow(x, y); 
		if (result > MAXRESULT)
		{
			System.err.println("calculatePowers result, " + result +
				" is too big.");
			result = 0;
		}
		// finish the method and pass the value in the memory location
		// named result back to the call site.
		return result;
	}
}