4.4 Tutorial 4 Four looping constructs

Question 4.4.1: Study, compile and run the following code:

class LoopTest
begin
    function int powerOf2A(int n)
    begin
        var int counter = n;
        var int result  = 1;
        while (counter > 0)
        begin
            result = 2 * result;
            counter = counter - 1;
        end
        return result;
    end

    function int powerOf2B(int n)
    begin
        var int counter = n;
        var int result  = 1;
        do
        begin
            result = 2 * result;
            counter = counter - 1;
        end while (counter > 0);
        return result;
    end

    function int powerOf2C(int n)
    begin
        var int result = 1;
        for (var int counter = n; counter > 0; counter = counter - 1)
        begin
            result = 2 * result;
        end
        return result;
    end

    function int powerOf2D(int n)
    begin
        var int result = 1;
        superfor (var int counter=n downto 1)
        begin
            result = 2 * result;
        end
        return result;
    end

     /**
      * Prints a row of stars of a given length.
      */
    function void printLineC(int length)
    begin
        for (var int i = 0; i<length; i=i+1)
        begin
            System.out.print("#");
        end
        System.out.println();
    end

    beginMain
        // For Question 4.4.1 add some code here...
    endMain
end

Question 4.4.2: To the main function add some code to call the functions powerOf2A, powerOf2B, powerOf2C and powerOf2D to verify that they all return the same result. To inspect the result you will need to apply the System.out.println() statement to the values returned by those functions.

Question 4.4.3: There is a bug in the powerOf2B function because it does not behave correctly in the case when n is zero or less. Put an if (...) then ... statement at the top of this function to make it handle the case of zero properly. Also make it return 1 in the case that n is less than zero.

Question 4.4.4: There is a bug in the powerOf2D function because it does not behave correctly in the case when n is zero or negative. Make it return 1 if n <= 0. Put an if (...) then ... statement at the top of this function to make it handle these cases properly. Since this function returns an int, make it return 1 in these cases.

Question 4.4.5: By copying the pattern of powerOf2A, powerOf2B, powerOf2C and powerOf2D, write functions printLineA, printLineB and printLineD that work identically to the function printLineC, except that they use while loops, do loops and superfor loops, respectively. Add some code to the main function to test them out.

Question 4.4.6: Based on the previous three questions, is there a best looping construct? Or does it depend on what the looping construct is going to be used for?