Expression evaluation in Rust - Mini Project: Build & Apply

Expression evaluation

📖 Scenario: You are building a simple calculator program that evaluates basic arithmetic expressions given as strings. This is useful for understanding how computers process math expressions step-by-step.

🎯 Goal: Create a Rust program that stores an arithmetic expression as a string, sets a variable for a number to use in the expression, evaluates the expression using that variable, and prints the result.

📋 What You'll Learn

Create a string variable called expression with the value "3 + x * 2".

Create an integer variable called x and set it to 4.

Calculate the result of the expression 3 + x * 2 using the variable x.

Print the result using println!.

💡 Why This Matters

🌍 Real World

Calculators, spreadsheets, and many software tools need to evaluate math expressions entered by users.

💼 Career

Understanding expression evaluation is important for programming tasks involving math, data processing, and building user input features.

1

DATA SETUP: Create the expression string

Create a string variable called expression and set it to the exact value "3 + x * 2".

Rust

# Create a string variable called expression with value "3 + x * 2"
// Your code here

Need a hint?

Use let expression = "3 + x * 2"; to create the string.

2

CONFIGURATION: Define the variable x

Create an integer variable called x and set it to 4.

Rust

let expression = "3 + x * 2";
// Create an integer variable x and set it to 4
// Your code here

Need a hint?

Use let x = 4; to create the variable.

3

CORE LOGIC: Evaluate the expression using x

Calculate the result of the expression 3 + x * 2 using the variable x and store it in a variable called result.

Rust

let expression = "3 + x * 2";
let x = 4;
// Calculate 3 + x * 2 and store in result
// Your code here

Need a hint?

Use let result = 3 + x * 2; to calculate the expression.

4

OUTPUT: Print the result

Print the value of the variable result using println!.

Rust

let expression = "3 + x * 2";
let x = 4;
let result = 3 + x * 2;
// Print the result
// Your code here

Need a hint?

Use println!("{}", result); inside fn main() to print the result.