Chapter 4 Exercise Set 0: Chapter Review

1. What happens if you call the countdown function introduced in the Recursion section with an argument that is a negative number?

2. Draw a stack diagram for n_lines, invoked with the parameter n equal to 4.

3. Write a function named compare that takes two int arguments, a and b, and prints out whether a is greater than b, a is less than b, or a is equal to b.

Exploring the bitwise operators

The following program will help you explore the bitwise operators:

#include <iostream>
using namespace std;

void print_byte_bits(unsigned char byte) {
    for (int mask = 128; mask > 0; mask >>= 1) {
        cout << (mask & byte ? '1' : '0');
        if (mask == 16) cout << ' ';
    }
    cout << endl;
}

void show_bitwise_operation(char byte1, char op, char byte2=0) {
    if (op == '~') {
        cout << "Showing ~" << int(byte1) << ':' << endl; 
        print_byte_bits(byte1);
        cout << "---------" << endl;
        print_byte_bits(~byte1);
        cout << endl;
        return;
    }
    if (op == 'l' || op == 'r') {
        cout << "Showing " << int(byte1) << ' ';
        cout << (op == 'l' ? "<< " : ">> ") << int(byte2) << ':' << endl;
        print_byte_bits(byte1);
        cout << "---------" << endl;
        if (op == 'l') print_byte_bits(byte1 << byte2);
        else print_byte_bits(byte1 >> byte2);
        cout << endl;
        return;
    }
    cout << "Showing " << int(byte1) << ' ' << op << ' ' << int(byte2);
    cout << ':' << endl; 
    print_byte_bits(byte1);
    print_byte_bits(byte2);
    cout << "---------" << endl;
    if (op == '&') print_byte_bits(byte1 & byte2);
    else if (op == '|') print_byte_bits(byte1 | byte2);
    else if (op == '^') print_byte_bits(byte1 ^ byte2);
    else if (op == 'l') print_byte_bits(byte1 << byte2);
    else if (op == 'r') print_byte_bits(byte1 >> byte2);
    cout << endl;
}

int main() {
    show_bitwise_operation(42, '&', 11);
    show_bitwise_operation(42, '|', 11);
    show_bitwise_operation(42, '^', 11);
    show_bitwise_operation(42, '~');
    show_bitwise_operation(42, 'l', 2);
    show_bitwise_operation(42, 'r', 2);
    return 0;
}

4. Compile and run this program and study its output.

5. Notice how the return statement is used to end execution of the show_bitwise_operation function in two places. Remove the two return statements and use chained conditionals instead, without changing the behavior of the function.

6. Add several additional calls to show_bitwise_operation with different operands and operators to explore these operators until you feel you understand what they do.

7. What happens to the least significant (rightmost) bit in a left shift operation? How about the most significant (leftmost) bit in a right shift operation?

Random numbers revisisted

8. Now that you know about the Modulus operator, use it to generate 3 random numbers between 1 and 10. This is a common algorithm, so do a web search for it if you need help figuring it out.