Mastering Rust - Second Edition

Functions

Functions abstract a bunch of instructions into named entities, which can be invoked later by other code and help manage complexity. We already used a function in our greet.rs program, that is, the main function. Let's look at how we can define another one:

// functions.rsfn add(a: u64, b: u64) -> u64 {    a + b}fn main() {    let a: u64 = 17;    let b = 3;    let result = add(a, b);    println!("Result {}", result);}

In the preceding code, we created a new function named add. The fn keyword is used to create functions followed by its name, add, its parameters inside parentheses a and b, and the function body inside {} braces. The parameters have their type on the right, after the colon :. Return types in functions are specified using a ->, followed ...