Function in Rust

We can group multiple statement/expression that do a certain thing in a function.

fn main() {   
    println!("Hello, world!");
 }

It’s written with fn //I like this! much shorter than writing funciton
Main function is like ‘the entry point’ for the program.

The naming convention use snake_case for multiple words.

fn main() {
    println!("Hello, world!");
    another_function();
}

fn another_function() {
    println!("Another function.");
}

Function parameters

A function can accept an argument. Declared with name: data type

fn main() {
    another_function(5);
}

fn another_function(x: i32) {
    println!("The value of x is: {}", x);
}

//For multiple parameters
fn another_function2(x: i32, y: i32) {
    println!("The value of x is: {}", x);
    println!("The value of y is: {}", y);
}

Function with return value

To return a value from a function, use arrow syntax like this

fn five() -> i32 {
    5
}

fn main() {
    let x = five();
    println!("The value of x is: {}", x);
}

//i32 is the data type of value we promise to return

Note, 5 has no semicolon at the end. It’s called an expression.

If we change it to a statement (has semicolon) it will return an error like this

error[E0308]: mismatched types

rust

Mon Sep 27, 2021

This is a post in the start learning Rust series.

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