Name. Classes and Objects 1. We re going to develop a class to help out Café Below is the definition for a class called

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1 Name CPTR246 Spring '17 (100 total points) Exam 1 Classes and Objects 1. We re going to develop a class to help out Café Below is the definition for a class called Beverage. The public and private sections of the class declaration are complete. You are to fill in the code for each member function, using the coded comments, along with your own experience in coding classes, as a guide to each function's use. (4 points for each function) /************************************************* * Beverage.h * *************************************************/ #include <string> #include <iomanip> using namespace std; class Beverage{ public: Beverage(string newdrink, char whichcup, string createdby); string setprices(double tall, double grande, double supreme); string whichcup(); void raiseprices(double increase); void makechange(int size, double payment); private: string name; // name of this beverage char cup; // which cup should be used ( H or C ) string developer; // name of the person who created the beverage double cost[3]; // cost for tall, grande, and supreme sizes ; Beverage::Beverage(string newdrink, char whichcup, string creator){ // Intent:Constructor // Pre: name, cup, and developer s name are provided as parameters // Post: data members initialized properly // NOTE: new drinks are initially FREE!!! 1

2 string Beverage::setPrices(double tall, double grande, double supreme){ // Intent: To set the prices of this drink // Pre: none // Post: data members are updated appropriately // NOTE: the array cost contains tall, grande, and supreme prices // in that order string Beverage::whichCup(){ // Intent: Returns which type of cup this beverage is to be served in. // Pre: none // Post: returns either hot or cold depending on the value of cup void Beverage::raisePrices(double increase){ // Intent: to raise the prices for this beverage // Pre: parameter increase is a percentage between 0.00 and 1.00 <----NOTE! // Post: data members updated properly // FOR FULL CREDIT, USE A for LOOP void Beverage::makeChange(int size, double payment){ // Intent: determine and display the amount of change for a beverage // bought with cash // pre: size is a 0, 1, or 2 to correspond with tall, grande, and venti, // respectively, and payment is how much the customer paid // post: displays the amount of change the customer should get back, // right-justified in a column of width 6 with 2 decimal positions 2

3 2. Using the class definition from question 1, give C++ code (1 line) to declare a Beverage object called mydrink. Give it any name you want as well as whether it is hot or cold, but you are to be the creator/developer of the beverage. (4 points) 3. Using the mydrink object that you defined in question 2 and the setprices method from the class definition in question 1, write code that will set the prices of the drink to $3.95, $4.95, and $5.95. (4 points) 4. Using the mydrink object that you defined in question 2 and the makechange method from the class definition in question 1, write code that will display on the screen the amount owed to a customer who pays with a $20.00 bill for a grande size. (4 points) Random Number Generation 5. Below is the prototype for the built-in function that generates a random number: int rand(); // returns an integer between 0 and RAND_MAX Complete the three assignment statements below so that variables x, y, and z have the values described in the comments. (Recall: the C++ remainder operator is % and C++ has the built-in value RAND_MAX.) (6 points) int x, y; double z; x = // a random integer between 0 and 15 y = // a random integer between -15 and 15 z = // a random real number between 0 and 1 3

4 Recursion 6. Write a recursive function named somefun that takes one parameter, an integer greater than or equal to 1 and returns an integer, given the following base and general cases. (6 points) Base case: somefun(1) = 3 General case: somefun(n) = (3 * somefun(n-1)) + 4 What would be returned by the function call somefun(4)? (4 points) True or False 7. For each of the following, indicate whether the statement is True or False by circling a T or an F, respectively. (4 points) T F When using the extraction operator (>>) to read from the keyboard or an input file, all leading whitespace is skipped, regardless of the type of data we are trying to read. T F When using the extraction operator (>>) to read a string from the keyboard or an input file, the entire string entered, up to and including the (the newline character inserted when the enter key is hit) is placed in the string. T F We can see what the next character that is in a buffer (either from cin or an input file) by calling the peek method. However we must use the putback method to put it back into the buffer. T F In C++, if a program tries to reference an element outside of an array, it will cause an ArrayOutOfBoundsException just as it does in Java. 4

5 Verifying input 8. Write code that prompts the user for an even integer, gets their response, and then checks to make sure that they did indeed enter an even integer. If they did not, display an appropriate message on the screen and allow the user to try again. Use a loop so that the program will not continue until the user enters an appropriate value. HINT: Even integers have a remainder of 0 when divided by 2 (think mod operator). (6 points) int n; // should be an even integer Call-by-value and Call-by-reference 9. What is the output of the following C++ code? Write the output below the program. (10 points) #include <iostream> using namespace std; void functiona(int & a, int b){ a = 5; b = 10; cout << a << " " << b << endl; void functionb(int & a, int b){ a = 15; b = 20; cout << a << " " << b << endl; int main() { int num1 = 100; int num2 = 200; cout << num1 << " " << num2 << endl; functiona (num1, num2); cout << num1 << " " << num2 << endl; functionb (num1, num2); cout << num1 << " " << num2 << endl; return 0; 5

6 File I/O 10. The program below read characters from the keyboard and counts how many of each letter occurs. Modify the code to take input from a file instead. Specifically, ask the user for the name of the file, open the file, terminate the program (with an appropriate error message) if the user enters an incorrect file name, and modify the remainder of the code to read the characters from the file. (8 points) #include <iostream> using namespace std; int main() { char letter; int lettercounts[26]; for (int i = 0; i < 26; i++) lettercounts[i] = 0; cin.get(letter); while (!cin.eof()) { letter = tolower(letter); if (letter >= 'a' && letter <= 'z') lettercounts[letter - 'a']++; cin.get(letter); for (int i = 0; i < 26; i++) cout << (char) (i + 'a') << "\t" << lettercounts[i] << endl; return 0; 6

7 Input Buffers and I/O States 11. Consider the following code: int x; cin >> x; a. Suppose the user entered 20 (note that signifies that the user hit the enter key and that the double quotes were not actually entered by the user). a. What would a subsequent call to cin.fail() return? (1 point) b. What would the subsequent expression (cin.peek()!= '\n') evaluate to. (1 point) b. Suppose the user entered 20.5 (note that signifies that the user hit the enter key and that the double quotes were not actually entered by the user). a. What would a subsequent call to cin.fail() return? (1 point) b. What would the subsequent expression (cin.peek()!= '\n') evaluate to. (1 point) c. Suppose the user entered five (note that signifies that the user hit the enter key and that the double quotes were not actually entered by the user). a. What would a subsequent call to cin.fail() return? (1 point) b. What would the subsequent expression (cin.peek()!= '\n') evaluate to. (1 point) 7

8 2-dimensional Arrays 12. Write the specified code in C++: Define a 2-dimensional array of integers named numbers with 20 rows and 15 columns. (3 points) Assume that the array numbers has been filled with integers. Write code that will add 10 to every value in the array. (5 points) 13. Write a free function called ismorepositive that takes two parameters, a two-dimensional array of integers with 15 columns and an integer for the number of rows in that array. It returns an integer. Specifically, it counts the number of positive values and negative values stored in the array. Zeroes are ignored. If the number of positive values is greater than the number of negative values, it returns a 1. If there are more negative values than positive, it returns a -1. If there are the same number of positive and negative values, it returns 0. (10 points) 8