Rust Functions Tutorial | Parameters & Return Values for Beginners (2026)

Rust Functions Tutorial | Parameters & Return Values for Beginners

Functions in Rust are defined using the fn keyword and allow you to organize code by encapsulating reusable logic. This tutorial covers creating basic functions, passing parameters (including string slices), and returning values using Rust’s concise syntax.

Code

// Basic function without parameters
fn greet() {
  println!("Hello from a function!");
}

// Function with a string slice parameter
fn greet(name: &str) {
  println!("Hello, {}!", name);
}

// Function with parameters and a return value
fn add(a: i32, b: i32) -> i32 {
  a + b  // No semicolon means this expression is returned
}

fn main() {
  greet();                  // Calls the basic greet function
  greet("Alice");           // Calls greet with a name parameter
  greet("Bob");             // Another call with a different name

  let sum = add(5, 3);      // Calls add and stores the returned value
  println!("5 + 3 = {}", sum);
}

Key Points

• Functions are declared with the fn keyword followed by the function name and parentheses.
• Parameters require explicit type annotations, such as name: &str for string slices.
• Return types are specified after an arrow -> before the function body.
• The last expression in a function without a semicolon is implicitly returned.
• The main() function serves as the entry point for Rust programs.