1. CMPT 201 if-else statement

3. Syntax for if-else if (condition) Yes_Statement else No_Statement
Chooses between two alternative actions

4. Boolean Expression The type bool Two possible values: true or false
bool flag;
Two possible values: true or false
1 < 2
2 > 3
number > 10
num1 < num2

5. Boolean Expression
if (number > 10) //when it is true cout<<“The number is greater than 10\n”; else //when it is false cout<<“The number is less than 10\n”;

6. Comparison Operators > greater than < less than
>= greater than or equal to
<= less than or equal to
== equal to
!= not equal to
a = 2;
if (a == 2)

7. Exercises
Read an integer from the user input, print a message showing if the number is even/odd.

9. Omitting the else part .... if (score < 60) score = 60;
cout<<“Your final score is ”<<score;

10. Exercise: Guess a number

11. The And Operator If score is greater than 0 and less than 100...
(score > 0) && (score < 100)
is true only if both are true

12. The Or Operator (score1 >= 60) || (score2 >= 60)
is true if one or both are true

13. The Not Operator
!(score > 60)
is equivalent to
score <= 60

14. What is the result of the following expression
!( (y < 3) || (y > 7) )
when y is 8?

15. Precedence Rules

16. if ((score > 0) && (score < 100))
even though the inner parentheses are not required
x + 1 > 2 || x + 1 < -3
((x + 1 ) > 2) || ((x + 1) < -3)
Arithmetic operators (highest)
Comparison operators
Logical operators

17. Note if (x < z < y ) // Wrong!!
cout<<“z is between x and y”;
if ((z > x) && (z < y))

18. Short-Circuit Evaluation
exp1 && exp2
if (((slices/students)>=2) && (students! =0))
cout<<“Each student may have two slices of pizza!”;
if ((students!=0) && ((slices/students)>=2))
cout<<“Each student may have two slices of pizza!”;

19. Nested Statements

20. Guess a Number (Validate the User Input)

21. Guess a Number

22. Find the right match!
if (fuel < 0.75) if (fuel < 0.25) cout<<“Fuel very low. Caution!”; else cout<<“Fuel over 3/4. Don’t stop now.”;

23. if (fuel < 0.75) {
if (fuel < 0.25)
cout<<“Fuel very low. Caution!”; }
else
cout<<“Fuel over 3/4. Don’t stop now.”;

24. Multiway if-else Sometimes things can not be solved in two ways.
Driver license example:
age<16: no way..
16<=age<18: youth license
18<=age<70: standard license
age>=70: special license

25. Multiway if-else syntax
if (condition_1)
Action_1;
else if (condition_2)
Action_2;
...
else if (condition_N)
Action_N;
else
Action_For_All_Other_Cases;

26. Under 16:
You have to wait
Between 16 and 18:
You may have a youth license
Between 18 and 70:
You may have a standard license
Over 70:
You need a special license

27. Exercise
Write a program to print the grade result based on the user input (score). Be sure to validate the user input. A
B 80-90
C 70-80
D 60-70
F <60

28. The Conditional Operator
Can be used to create short if/else statements
Format: expr ? expr : expr;
x<0 ? y=10 : z=20;
First Expression:
Expression to be
tested
2nd Expression:
Executes if first
expression is true
3rd Expression:
Executes if the first
expression is false

29. x > 100? a = 0 : a = 1
a = x > 100 ? 0 : 1

30. Blocks and Scope
Scope of a variable is the block in which it is defined.

31. Type Casting static_cast<Type>(Value) double -> int
static_cast<int>(9.2)
static_cast<int>(number)

32. Type Casting (cont.) double m; m = static_cast<double>(y2-y1)
Useful for floating point division using ints:
double m; m = static_cast<double>(y2-y1)
/(x2-x1);
Useful to see int value of a char variable:
char ch = 'C';
cout << ch << " is "
<< static_cast<int>(ch);

33. Comparing Characters Characters are compared using their ASCII values.
'A' < 'B'
The ASCII value of 'A' (65) is less than the ASCII value of 'B'(66)
How could you determine if a character is a capital letter?
Lowercase letters have higher ASCII codes than uppercase letters, so 'a' > 'Z'

34. Homework 2
Due on Tuesday, October 4