Learning Rust: Variables & Types

// variables1.rs - got this first try
let x = 5; 

// variables2.rs - just add mut
let mut x = 5;
x = 6;

// variables3.rs - type annotation
let x: i32 = 42;

// Numbers from primitives1.rs
let a: i32 = -15;   
let b: u32 = 120;   
let c = 1000;       // i32 by default

// Quick note on signed vs unsigned:
// i8: -128 to 127 (can store negative)
// u8: 0 to 255 (only positive)
// Same pattern for i16/u16, i32/u32, i64/u64
// u = unsigned (≥0), i = signed (+ or -)

// Chars/bools from primitives2.rs 
let my_char = 'x';
let is_true = false;

// strings1.rs
let word = String::from("green");     // needed .from()
let string_slice = "blue";            // &str literal

// strings2.rs 
let word = String::from("green");
&word                                 // borrowing - more on this later

// Creating vectors
let v: Vec<i32> = Vec::new();        // empty vector
let v = vec![1, 2, 3];               // with macro
let mut v = Vec::new();              // mutable empty vector

// Adding elements (if mutable)
v.push(4);
v.push(5);

// Accessing elements - two ways:
let third = &v[2];                   // might panic if index out of bounds
let third = v.get(2);                // returns Option<&T>

// Iterating
for i in &v {
    println!("{}", i);
}

// Common methods
v.pop();                             // removes and returns last element
v.len();                             // get length
v.clear();                           // remove all elements