leeebo/learning_rs

Learning Rust with C basics

Learning Rust with C basics

Hello, World!

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

1. fn keyword is used to declare a function
2. main function is the entry point of the program
3. ! indicates that println is a macro, not a function
4. println! is a macro that prints text to the console

Variables and Mutability

let x = 5;
let y: i32 = 10;
let mut z = 15.0;
let y = "Hello, World!"; // shadowing

1. using let to declare a variable
2. using : after the variable name to specify the type of the variable (optional)
3. variables are immutable by default
4. using mut to make a variable mutable
5. variables can be shadowed

Data Types

let x = 0b1101_1010;
let c = '😆';
let t = (1, 2.0, "three");
// same with let t: (i32, f32, &str) = (1, 2.0, "three");
let a = [1, 2, 3, 4, 5];

1. _ can be used as a visual separator for large numbers
2. char type represents a single Unicode character, which is 4 bytes in size
3. tuple type can be used to group multiple values of different types
4. array type has a fixed length and all elements must have the same type

index out of bounds error will be thrown at runtime if the index is out of bounds

Functions

fn addi32(x: i32, y: i32) -> i32 {
    x + y
}

fn main() {
    let x = 5;
    let y = 10;
    let z = addi32(x, y);
    println!("{} + {} = {}", x, y, z);
}

1. functions are declared using the fn keyword
2. function's parameters must have type annotations, eg. x: i32
3. function's return type using annotations, eg. -> i32
4. statements not returning a value, x=y=5; is not allowed
5. expressions do not include ending semicolons, x+y is an expression, x+y; is a statement