Understanding function

Understanding functions syntax

• Functions are declared using fn keyword
• Use snake case for function names, e.g., say_hello (recommended)
• A function can be declared after using it, so order is not important, like JavaScript
• We don't have named parameters, so order is important when passing the parameters

Simple function

fn main() {
    say_hello()
}

fn say_hello() {
    let message = "hello world";
    println!("{}", message);
}

Function parameters

• Return type is denoted by ->

fn main() {
    let result = add_both(2, 5);
    println!("Result: {}", result)
}

fn add_both(a: i32, b: i32) -> i32 {
    return a + b;
}

Tail expression (Shorthand)

• If you leave ; off the last expression of a block, then it will be returned as the value of the block.

fn main() {
    let result = add_both(2, 5);
    println!("Result: {}", result)
}

fn add_both(a: i32, b: i32) -> i32 {
    a + b
}

Macros

• They look like function
• Macros accept variable number of arguments
• Name of macro ends with !
• println! is a macro