Lab_Week2

CPS 216,

Problem Solving and Programming Techniques in C++

Saleh M. Alnaeli, Ph.D.

Spring, 2016

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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

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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.

• *,/,+,-,%

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Exercise 1: Expressions (2.1)

• Write the results of each of the following expressions. If you're stuck, ask me or your neighbor

• 12 / 5 + 8 / 4 =

• 3 * 4 + 15 / 2 =

• -(1 + 2 * 3 + (1 + 2) * 3) =

• 42 % 5 + 16 % 3 =

• 2.5 * 2 + 17 / 4 =

• 4.5 / 3 / 2 + 1 =

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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 / 5 + 8 / 4 = 4

• 3 * 4 + 15 / 2 = 19

• -(1 + 2 * 3 + (1 + 2) * 3) = -16

• 42 % 5 + 16 % 3 = 3

• 2.5 * 2 + 17 / 4 = 9.0

• 4.5 / 3 / 2 + 1 = 1.75

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Exercise 2: More expressions (2.1)

• Write the results of each of the following expressions.

• 2 + 6 + "cse 142" =

• "cse 142" + 2 + 6 =

• 1 + 9 / 2 * 2.0 =

• 46 / 3 / 2.0 / 3 * 4/5 =

• 50 / 9 / 2.0 + 200 / 10 / (5.0 / 2) =

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Exercise 2: More expressions (2.1) Answers

• Write the results of each of the following expressions.

• 2 + 6 + "cse 142" = Unpredictable

• "cse 142" + 2 + 6 = Unpredictable

• 1 + 9 / 2 * 2.0 = 9

• 46 / 3 / 2.0 / 3 * 4/5 = 2

• 50 / 9 / 2.0 + 200 / 10 / (5.0 / 2) = 10.5

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VariablesRecall that you can use a variable to store the results of an expression in memory and use them later in the program.

type name; // declare

name = value or expression; // assign a value

...

type name = value or expression; // declare-and-initialize together

Examples: double iphonePrice;

iPhonePrice = 299.95;

int siblings = 3;

cout<< "I have " << siblings << " brothers/sisters. " << endl;

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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;

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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;

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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;

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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;

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Exercise 5: Variable mutation

Suppose you have a variable named balance, set to 463.23:

double balance = 463.23

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;

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Exercise 5: Variable mutation

Suppose you have a variable named balance, set to 463.23:

double balance = 463.23

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;

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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?

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answers

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?

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answers

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9

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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;

4.

5. int x = 15.2; // set x to 15.2

6. cout<<"x is now :" + x<<endl;

7.

8. 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

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?

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answers

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?

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answers

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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 = 12.3x4 - 9.1x3 + 19.3x2 - 4.6x + 34.2

• Note: (We haven't learned a way to do exponents yet, but you can simulate them using several multiplications.)

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Exercise 9- Example codeCopy/paste this program into MSVS to test your solution. // expected output:// y is 7043.7// y = 12.3x4 - 9.1x3 + 19.3x2 - 4.6x + 34.2

Int main(){double x = 5;

double y = put your expression for y here ;cout<<"y is " << y<<endl;

}

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Exercise 9- Example codeCopy/paste this program into MSVS to test your solution.

// expected output:

// y is 7043.7

// y = 12.3x4 - 9.1x3 + 19.3x2 - 4.6x + 34.2

Int main(){

double x = 5;

double y = 12.3*x*x*x*x - 9.1*x*x*x + 19.3*x*x - 4.6*x + 34.2;

cout<<"y is " << y<<endl;

}

// Refactoring , source code improvement with same outputs

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Exercise 9- Example codeCopy/paste this program into MSVS to test your solution.

// expected output:

// y is 7043.7

// y = 12.3x4 - 9.1x3 + 19.3x2 - 4.6x + 34.2

Int main(){

double x = 5;

double y = (((12.3 * x - 9.1) * x + 19.3) * x - 4.6) * x + 34.2;

cout<<"y is " << y<<endl;

}

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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.

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Exercise 11: Syntax errorsThe 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= 10000 * 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

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? 95 89.5 94.5 100

Your GPA is 94.75

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Exercise 12: GPA Solution

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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 2.77778

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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

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Thank you

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References• Building Java Programs, A BACK TO BASICS APPROACH

• (6th Edition), 2015

• by Stuart Reges and Marty Stepp, from University of Washington

• ISBN-10: 0133360903; ISBN-13: 9780133360905

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