CPS 216, Problem Solving and Programming Techniques in C++ Saleh M. Alnaeli, Ph.D. Spring, Lab_Week2

Transcription

1 CPS 216, Problem Solving and Programming Techniques in C++ Saleh M. Alnaeli, Ph.D. Spring, 2016 Lab_Week2 1

2 My goals Goals for this problem set: write and evaluate expressions to compute numeric values use variables to store results of a computation into memory use cin to create interactive programs that read user input use Strings to represent and manipulate text data 2

3 Expressions Recall that cin has expressions to represent math and other computations. Expressions may use operators, which are evaluated according to rules of precedence. Every expression produces a value of a given type. Ex: int, double, bool, char. *,/,+,-,% 3

4 Exercise 1: Expressions (2.1) Write the results of each of the following expressions. If you're stuck, ask me or your neighbor 12 / / 4 = 3 * / 2 = -(1 + 2 * 3 + (1 + 2) * 3) = 42 % % 3 = 2.5 * / 4 = 4.5 / 3 / = 4

5 Exercise 1: Expressions (2.1) Answers Write the results of each of the following expressions. If you're stuck, ask me or your neighbor 12 / / 4 = 4 3 * / 2 = 19 -(1 + 2 * 3 + (1 + 2) * 3) = % % 3 = * / 4 = / 3 / =

6 Exercise 2: More expressions (2.1) Write the results of each of the following expressions "cse 142" = "cse 142" = / 2 * 2.0 = 46 / 3 / 2.0 / 3 * 4/5 = 50 / 9 / / 10 / (5.0 / 2) = 6

7 Exercise 2: More expressions (2.1) Answers Write the results of each of the following expressions "cse 142" = Unpredictable "cse 142" = Unpredictable / 2 * 2.0 = 9 46 / 3 / 2.0 / 3 * 4/5 = 2 50 / 9 / / 10 / (5.0 / 2) =

8 Variables Recall that you can use a variable to store the results of an expression in memory and use them later in the program. type name; name = value or expression;... // declare // assign a value type name = value or expression; // declare-and-initialize together Examples: double iphoneprice; iphoneprice = ; int siblings = 3; cout<< "I have " << siblings << " brothers/sisters. " << endl; 8

9 Exercise 3: Variable declaration syntax Which of the following choices is the correct syntax for declaring a real number variable named grade and initializing its value to 4.0? a. int grade = 4.0; b. grade = 4.0; c. 4.0 = grade; d. grade : 4.0; e. grade = double 4.0; f. double grade = 4.0; 9

10 Exercise 3: Variable declaration syntax Which of the following choices is the correct syntax for declaring a real number variable named grade and initializing its value to 4.0? a. int grade = 4.0; b. grade = 4.0; c. 4.0 = grade; d. grade : 4.0; e. grade = double 4.0; f. double grade = 4.0; 10

11 Exercise 4: Variable assignment syntax Suppose you have a variable named grade, set to 1.6: double grade = 1.6; // uh-oh Suppose later in the program's code, we want to change the value of grade to 4.0. Which is the correct syntax to do this? a. grade : 4.0; b. set grade = 4.0; c. grade = 4.0; d. double grade = 4.0; e. 4.0 = grade; 11

12 Exercise 4: Variable assignment syntax Suppose you have a variable named grade, set to 1.6: double grade = 1.6; // uh-oh Suppose later in the program's code, we want to change the value of grade to 4.0. Which is the correct syntax to do this? a. grade : 4.0; b. set grade = 4.0; c. grade = 4.0; d. double grade = 4.0; e. 4.0 = grade; 12

13 Exercise 5: Variable mutation Suppose you have a variable named balance, set to : double balance = Suppose later in the program's code, we want to add 5 to the account balance. Which is a correct statement to do this? a. balance <-- 5; b. 5 + balance = balance; c. balance + 5; d. balance = balance + 5; e. balance = 5; 13

14 Exercise 5: Variable mutation Suppose you have a variable named balance, set to : double balance = Suppose later in the program's code, we want to add 5 to the account balance. Which is a correct statement to do this? a. balance <-- 5; b. 5 + balance = balance; c. balance + 5; d. balance = balance + 5; e. balance = 5; 14

15 Exercise 6: a, b, and c What are the values of a, b, and c after the following statements? Write your answers in the boxes on the right. int a = 5; int b = 10; int c = b; a = a + 1; // a? b = b - 1; // b? c = c + a; // c? answers 15

16 Exercise 6: a, b, and c What are the values of a, b, and c after the following statements? Write your answers in the boxes on the right. int a = 5; int b = 10; int c = b; a = a + 1; // a? b = b - 1; // b? c = c + a; // c? answers

17 Exercise 7: Syntax errors The following program contains multiple mistakes! What are they? Copy and paste the following code into MSVS and correct the various mistakes. I will provider the answer in 5 minutes. Work in pairs 1. int main(){ 2. int x; 3. cout<< "x is" x<<endl; int x = 15.2; // set x to cout<<"x is now :" + x<<endl; int y; // set y to 1 more than x 9. y = int x + 1; 10. cout<<"x and y are " + x + and + y<< \n ; 11. } 17

18 Exercise 8: i, j, and k What are the values of i, j, and k after the following statements? int i = 2; int j = 3; int k = 4; int x = i + j + k; i = x - i - j; // i? j = x - j - k; // j? k = x - i - k; // k? answers 18

19 Exercise 8: i, j, and k What are the values of i, j, and k after the following statements? int i = 2; int j = 3; int k = 4; int x = i + j + k; i = x - i - j; // i? j = x - j - k; // j? k = x - i - k; // k? answers

20 Exercise 9: Equation Suppose you have a real number variable x. Write a c++ expression that computes a variable named y storing the following value: y = 12.3x 4-9.1x x 2-4.6x Note: (We haven't learned a way to do exponents yet, but you can simulate them using several multiplications.) 20

21 Exercise 9- Example code Copy/paste this program into MSVS to test your solution. // expected output: // y is // y = 12.3x 4-9.1x x 2-4.6x Int main(){ double x = 5; double y = put your expression for y here ; cout<<"y is " << y<<endl; } 21

22 Exercise 9- Example code Copy/paste this program into MSVS to test your solution. // expected output: // y is // y = 12.3x 4-9.1x x 2-4.6x Int main(){ double x = 5; double y = 12.3*x*x*x*x - 9.1*x*x*x *x*x - 4.6*x ; cout<<"y is " << y<<endl; } // Refactoring, source code improvement with same outputs 22

23 Exercise 9- Example code Copy/paste this program into MSVS to test your solution. // expected output: // y is // y = 12.3x 4-9.1x x 2-4.6x Int main(){ double x = 5; double y = (((12.3 * x - 9.1) * x ) * x - 4.6) * x ; cout<<"y is " << y<<endl; } 23

24 Exercise 10: Birthday variables Create a complete C++ program that declares four variables and assigns appropriate values to them. your birthday month (1-12) your birthday day (1-31) the birthday month of another student sitting near you today (1-12) the birthday day of that same student near you (1-31) Ask your neighbor (if any ) for their name and for the proper numbers to store in the variables for his/her birthday. Then produce output in this format using your four variables: My birthday is 9/19, and Suzy's is 6/14. 24

25 Exercise 11: Syntax errors The following CPP program has multiple errors. Can you find them all? 1. Int main() { 2. cout<< "Type your name: "; 3. String name; 4. cin>> name ; 5. cout>>"you must be really awesome."; 6. int mypartpercent=2.5; 7. double mynetpart= * mypartpercent; 8. cout<< my net part is + mynetpart<<\n; 9. } Copy and paste the code into MSVS and see if you can fix the errors. 25

26 Exercise 12: GPA Write a complete program MyGPA that reads a student 4 grades and prints her GPA. You can assume that all courses have equal credit hours. Use the cin to read user input for a student's grades Program s behavior is shown below : Please enter 4 grades? Your GPA is

27 Exercise 12: GPA Solution 27

28 Exercise 13: temperature converter Write a complete program TempConvert that reads a temperature in Fahrenheit and prints it in Celsius. Formula: Celsius= (Fahrenheit-32)* (5.0/9.0) ; Use the cin to read user input for a temperature in Fahrenheit Program s behavior is shown below : please enter your temperature in Fahrenheit --> 37 Temperature in Celsius is

29 What s Coming Up Soon Assignment 2: Exercise 12 and 13 (slides 26 and 28). Will be posted this evening. Due date: Saturday 6th, 7:00 PM 1: Quiz 1, Sunday on D2L 29

30 Thank you 30

31 References Building Java Programs, A BACK TO BASICS APPROACH (6th Edition), 2015 by Stuart Reges and Marty Stepp, from University of Washington ISBN-10: ; ISBN-13: