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Programming with M-Files: If-Statement Drill Exercises

Module by: Darryl Morrell. E-mail the author

Summary: This module provides several simple exercises designed to test and increase your understanding of if statements in m-file scripts.

Some If Statement Exercises

Exercise 1

What will the following code print?


a = 10;
if a ~= 0
    disp('a is not equal to 0')
end

Solution

' a is not equal to 0'

Exercise 2

What will the following code print?


a = 10;
if a > 0
    disp('a is positive')
else
    disp('a is not positive')
end

Solution

' a is positive'

Exercise 3

What will the following code print?


a = 5;
b = 3;
c = 2;
if a < b*c
    disp('Hello world')
else
    disp('Goodbye world')
end

Solution

b*c gives a value of 6, and 5 < 6, so this code will print 'Hello world'.

Exercise 4

Suppose the code in Exercise 2 is modified by adding parentheses around a > 0. What will it print?


a = 10;
if (a > 0)
    disp('a is positive')
else
    disp('a is not positive')
end

Solution

The parentheses around the relational expression a > 0 will not change its validity, so this code will print 'a is positive'.

Exercise 5

Suppose the code in Exercise 3 is modified by adding the parentheses shown below. What will it print?


a = 5;
b = 3;
c = 2;
if (a < b)*c
    disp('Hello world')
else
    disp('Goodbye world')
end

Solution

The parentheses in this expression change its meaning completely. First, a < b is evaluated, and since it is false for the given values of a and b, it evaluates to zero. The zero is than multiplied by c, giving a value of zero which is interpreted as false. So this code prints 'Goodbye world'.

Exercise 6

What will the following code print?


p1 = 3.14;
p2 = 3.14159;
if p1 == p2
    disp('p1 and p2 are equal')
else
    disp('p1 and p2 are not equal')
end

Solution

' p1 and p2 are not equal'

Exercise 7

What will the following code print?


a = 5;
b = 10;
if a = b
    disp('a and b are equal')
else
    disp('a and b are not equal')
end

Solution

This code will generate an error message, since a = b assigns the value of b to a. To check if a and b are equal, use a == b.

Exercise 8

For what values of the variable a will the following MATLAB code print 'Hello world'?


if ~ a == 0
    disp('Hello world')
else
    disp('Goodbye world')
end

Solution

Any value that is not zero.

Exercise 9

For what values of the variable a will the following code print 'Hello world'?


if a >= 0 && a < 7
    disp('Hello world')
else
    disp('Goodbye world')
end

Solution

Any value greater than or equal to 0 and less than 7.

Exercise 10

For what values of the variable a will the following code print 'Hello world'?


if a < 3 || a > 10
    disp('Hello world')
else
    disp('Goodbye world')
end

Solution

Any value less than 3 or greater than 10.

Exercise 11

For what values of the variable a will the following code print 'Hello world'?


if a < 7 || a >= 3
    disp('Hello world')
else
    disp('Goodbye world')
end

Solution

Every value of a will print 'Hello world'.

Exercise 12

Write an if statement that will print 'a is very close to zero' if the value of the variable a is between -0.01 and 0.01.

Solution


        
if a >= -0.01 && a <= 0.01
    disp('a is very close to zero')
end

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