Operator precedence in MATLAB - Mini Project: Build & Apply

Operator precedence

📖 Scenario: Imagine you are calculating the total cost of items in a shopping cart with discounts and taxes applied. The order in which you perform these calculations matters to get the correct final price.

🎯 Goal: You will write MATLAB code to calculate the final price of an item by applying discounts and taxes, demonstrating how operator precedence affects the result.

📋 What You'll Learn

Create variables with exact values for price, discount rate, and tax rate

Create a variable for the discounted price using correct operator precedence

Calculate the final price by adding tax to the discounted price

Display the final price using disp

💡 Why This Matters

🌍 Real World

Calculating prices with discounts and taxes is common in shopping apps and billing systems.

💼 Career

Understanding operator precedence helps avoid bugs in financial calculations and data processing tasks.

1

Create initial variables

Create a variable called price and set it to 100. Create a variable called discount and set it to 0.2 (which means 20%). Create a variable called tax and set it to 0.1 (which means 10%).

MATLAB

% Your code here

Hint

Use the assignment operator = to set the variables.

2

Calculate discounted price

Create a variable called discounted_price that calculates the price after discount by subtracting price * discount from price. Use parentheses to ensure the multiplication happens before subtraction.

MATLAB

price = 100;
discount = 0.2;
tax = 0.1;
% Your code here

Hint

Remember multiplication has higher precedence than subtraction, but use parentheses to be clear.

3

Calculate final price with tax

Create a variable called final_price that adds tax to the discounted_price. Multiply discounted_price by tax and add it to discounted_price. Use parentheses to ensure multiplication happens before addition.

MATLAB

price = 100;
discount = 0.2;
tax = 0.1;
discounted_price = price - (price * discount);
% Your code here

Hint

Use parentheses to make sure the multiplication happens before the addition.

4

Display the final price

Use disp to display the value of final_price.

MATLAB

price = 100;
discount = 0.2;
tax = 0.1;
discounted_price = price - (price * discount);
final_price = discounted_price + (discounted_price * tax);
% Your code here

Hint

Use disp(final_price) to show the result.

Practice

1. In MATLAB, which operator has the highest precedence in the expression 3 + 4 * 2?

easy

A. Subtraction (-)

B. Addition (+)

C. Division (/)

D. Multiplication (*)

Solution

1. Step 1: Recall operator precedence rules

   Multiplication and division have higher precedence than addition and subtraction in MATLAB.

2. Step 2: Apply precedence to the expression

   In 3 + 4 * 2, multiplication happens first, so 4 * 2 = 8, then addition: 3 + 8 = 11.

3. Final Answer:

   Multiplication (*) -> Option D

4. Quick Check:

   Multiplication before addition = Multiplication (*) [OK]

Hint: Multiply/divide before add/subtract unless parentheses used [OK]

Common Mistakes:

• Adding before multiplying
• Ignoring operator precedence
• Assuming left-to-right always applies

2. Which of the following MATLAB expressions correctly uses parentheses to ensure addition happens before multiplication?

easy

A. 3 + (4 * 2)

B. 3 + 4 * 2

C. (3 + 4) * 2

D. 3 * 4 + 2

Solution

1. Step 1: Understand parentheses effect

   Parentheses force MATLAB to calculate inside them first, overriding normal precedence.

2. Step 2: Check each expression

   Only (3 + 4) * 2 adds 3 and 4 first, then multiplies by 2.

3. Final Answer:

   (3 + 4) * 2 -> Option C

4. Quick Check:

   Parentheses change order = (3 + 4) * 2 [OK]

Hint: Use parentheses to change normal operator order [OK]

Common Mistakes:

• Ignoring parentheses effect
• Assuming multiplication always first
• Misplacing parentheses

3. What is the output of the following MATLAB code?

a = 5 + 3 * 2 / 6 - 1;

medium

A. 5.0

B. 6

C. 6.0

D. 5

Solution

1. Step 1: Calculate multiplication and division first

   Calculate 3 * 2 = 6, then 6 / 6 = 1.

2. Step 2: Perform addition and subtraction left to right

   Expression becomes 5 + 1 - 1, which is 5.0.

3. Final Answer:

   5.0 -> Option A

4. Quick Check:

   Multiply/divide first, then add/subtract = 5.0 [OK]

Hint: Multiply/divide before add/subtract, left to right [OK]

Common Mistakes:

• Adding before multiplying
• Ignoring division precedence
• Confusing integer and floating-point output

4. Identify the error in this MATLAB expression:

result = 4 + * 3;

medium

A. No error, valid expression

B. Syntax error due to misplaced operator

C. Runtime error due to undefined variable

D. Logical error in calculation

Solution

1. Step 1: Analyze the expression syntax

   The expression 4 + * 3 has two operators '+' and '*' without a number between them, which is invalid syntax.

2. Step 2: Confirm MATLAB error type

   MATLAB will throw a syntax error because the operator '*' cannot directly follow '+'.

3. Final Answer:

   Syntax error due to misplaced operator -> Option B

4. Quick Check:

   Operators must have operands between them [OK]

Hint: Check operators have numbers on both sides [OK]

Common Mistakes:

• Assuming expression is valid
• Ignoring operator placement rules
• Confusing syntax and runtime errors

5. Given the MATLAB expression:

value = 10 - 2 * (3 + 1) / 2 + 4;

What is the correct value of value after MATLAB evaluates it?

hard

A. 10

B. 8

C. 6

D. 12

Solution

1. Step 1: Calculate inside parentheses first

   (3 + 1) = 4.

2. Step 2: Perform multiplication and division next

   Calculate 2 * 4 = 8, then 8 / 2 = 4.

3. Step 3: Perform addition and subtraction left to right

   Expression becomes 10 - 4 + 4. Since + and - have same precedence and are left-associative: 10 - 4 = 6, then 6 + 4 = 10.

4. Final Answer:

   10 -> Option A

5. Quick Check:

   Parentheses, then multiply/divide, then add/subtract = 10 [OK]

Hint: Calculate parentheses first, then multiply/divide, then add/subtract [OK]

Common Mistakes:

• Adding before subtracting
• Ignoring parentheses
• Doing operations out of order