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

#Compiling and Running

$ rustc Hello_World.rs
  $ ./Hello_World
  Hello, World!
  

See: Rust Types

// Prints the output
  print!("Hello World\n");
  
  // Appends a new line after printing
  println!("Appending a new line");
  
  // Prints as an error
  eprint!("This is an error\n");
  
  // Prints as an error with new line
  eprintln!("This is an error with new line");
  

// Initializing and declaring a variable
  let some_variable = "This_is_a_variable";
  
  // Making a variable mutable
  let mut mutable_variable = "Mutable";
  
  // Assigning multiple variables
  let (name, age) = ("ElementalX", 20);
  
  // (Global) constant
  const SCREAMING_SNAKE_CASE:i64 = 9;
  

// Line Comments
  /*.............Block Comments */
  /// Outer doc comments
  //! Inner doc comments
  

See: Comment

fn test(){
    println!("This is a function!");
  }
  
  fn main(){
    test();
  }
  

See: Functions

let mut a: u32 = 8;
  let b: u64 = 877;
  let c: i64 = 8999;
  let d = -90;
  

let mut sixty_bit_float: f64 = 89.90;
  let thirty_two_bit_float: f32 = 7.90;
  let just_a_float = 69.69;
  

let true_val: bool = true;
  let false_val: bool = false;
  let just_a_bool = true;
  let is_true = 8 < 5;  // => false
  

let first_letter_of_alphabet = 'a';
  let explicit_char: char = 'F';
  let implicit_char = '8';
  let emoji = "\u{1f600}";   // => 😀
  

let community_name = "AXIAL";
  let no_of_members: &str = "ten";
  
  println!("The name of the community is {community_name} and it has {no_of_members} members");
  

See: Strings

┌─────┬─────┬─────┬─────┬─────┬─────┐
  | 92  | 97  | 98  | 99  | 98  | 94  |
  └─────┴─────┴─────┴─────┴─────┴─────┘
     0     1     2     3     4     5
  

let array: [i64; 6] = [92,97,98,99,98,94];
  

let mut array: [i32 ; 3] = [2,6,10];
  
  array[1] = 4;
  array[2] = 6;
  

Use the mut keyword to make it mutable.

let mut array: [ i64; 4] = [1,2,3,4];
  let mut slices: &[i64] = &array[0..3] // Lower range is inclusive and upper range is exclusive
  
  println!("The elements of the slices are : {slices:?}");
  

let some_vector = vec![1,2,3,4,5]; 
  

A vector is declared using the vec! macro.

let tuple = (1, 'A' , "Cool", 78, true);
  

let cs:&str = "cheat sheet";
  
  // => Share cheat sheet for developers
  println!("Share {cs} for developers");
  

// Creating an empty string object
  let my_string = String::new;
  
  // Converting to a string object
  let S_string = a_string.to_string()
  
  // Creating an initialized string object
  let lang = String::from("Rust");  
  println!("First language is {lang}");
  

let rand = String::from("Random String");
  rand.capacity()  // => 13
  

Calculates the capacity of the string in bytes.

let name = String::from("ElementalX");
  name.contains("Element") // => true
  

Checks if the substring is contained inside the original string or not.

let mut half_text = String::from("Hal");
  half_text.push('f');    // => Half
  

let mut hi = String::from("Hey there...");
  hi.push_str("How are you doing??");
  
  // => Hey there...How are you doing??
  println!("{hi}");
  

let (e, f) = (1, 100);
  
  let greater = f > e;        // => true
  let less = f < e;           // => false
  let greater_equal = f >= e; // => true
  let less_equal = e <= f;    // => true
  let equal_to = e == f;      // => false
  let not_equal_to = e != f;  // => true
  

let (a, b) = (4, 5);
  
  let sum: i32 = a + b;            // => 9
  let subtractions: i32 = a - b;   // => -1
  let multiplication: i32 = a * b; // => 20
  let division: i32 = a / b;       // => 0
  let modulus: i32 = a % b;        // => 4
  

let (g, h) = (0x1, 0x2);
  
  let bitwise_and = g & h;  // => 0
  let bitwise_or = g | h;   // => 3
  let bitwise_xor = g ^ h;  // => 3
  let right_shift = g >> 2; // => 0
  let left_shift = h << 4;  // => 32 
  

let (c, d) = (true, false);
  
  let and = c && d;  // => false
  let or  = c || d;  // => true
  let not = !c;      // => false
  

let mut k = 9;
  let mut l = k;
  

let case1: i32 = 81;
  let case2: i32 = 82;
  
  if case1 < case2 {
    println!("case1 is greater than case2");
  }
  

let case3 = 8;
  let case4 = 9;
  
  if case3 >= case4 {
    println!("case3 is better than case4");
  } else {
    println!("case4 is greater than case3");
  }
  

let foo = 12;
  let bar = 13;
  
  if foo == bar {
    println!("foo is equal to bar");
  } else if foo < bar {
    println!("foo less than bar");
  } else if foo != bar {
    println!("foo is not equal to bar");
  } else {
    println!("Nothing");
  }
  

let nested_conditions = 89;
  if nested_conditions == 89 {
      let just_a_value = 98;
      if just_a_value >= 97 {
          println!("Greater than 97");
      }
  }
  

for mut i in 0..15 {
    i-=1;
    println!("The value of i is : {i}");
  }
  

let mut check =  0;
  while check < 11{
    println!("Check is : {check}");
    check+=1;
    println!("After incrementing: {check}");
  
    if check == 10{
      break; // stop while
    }
  }
  

loop {
    println!("hello world forever!");
  }
  

The infinite loop indicated.

let mut i = 1;
  loop {
    println!("i is {i}");
    if i > 100 {
      break;
    }
    i *= 2;
  }
  

for (v, c) in (0..10+1).enumerate(){
    println!("The {c} number loop");
    if v == 9{
      println!("Here we go continue?");
      continue;
    }
    println!{"The value of v is : {v}"};
  }
  

  fn print_message(){
    println!("Hello, CareerInEdu!");
  }
  
  fn main(){
    //Invoking a function in Rust.
    print_message();
  }
  

fn main()
  {
    let x:u32 = 10;
    let y:u32 = 20;
    
    // => 200
    println!("Calc: {}", cal_rect(x, y));
  }
  fn cal_rect(x:u32, y:u32) -> u32
  {
    x * y
  }
  

fn main(){
    let mut by_ref = 3;      // => 3
    power_of_three(&mut by_ref);
    println!("{by_ref}");  // => 9
  }
  
  fn power_of_three(by_ref: &mut i32){
    // de-referencing is important
    *by_ref = *by_ref * *by_ref;
    println!("{by_ref}");  // => 9
  }
  

fn main(){
    let (mut radius, mut pi) = (3.0, 3.14);
    let(area, _perimeter) = calculate (
        &mut radius,
        &mut pi
    );
    println!("The area and the perimeter of the circle are: {area} & {_perimeter}");
  }
  
  fn calculate(radius : &mut f64, pi: &mut f64) -> (f64, f64){
    let perimeter = 2.0 * *pi * *radius;
    let area = *pi * *radius * *radius;
    return (area, perimeter);
  }
  

fn main(){
    let mut array: [i32 ; 5] = [1,2,3,4,6];
    print_arrays(array);
    println!("The elements: {array:?}");
  }
  
  fn print_arrays(mut array:[i32; 5]) {
    array[0] = 89;
    array[1] = 90;
    array[2] = 91;
    array[3] = 92;
    array[4] = 93;
    println!("The elements: {array:?}");
  }
  

  fn main(){
    let mut arr:[i32; 5] = [2,4,6,8,10];
    multiply(arr);
    println!("The array is : {:?}", multiply(arr));
  }
  
  fn multiply (mut arr: [i32 ; 5]) -> [i32 ; 5]{
    arr[2] = 90;
    for mut i in 0..5 {
        arr[i] = arr[i] * arr[2];
    }
    return arr;
  }
  

let a_int = 90; // int
  // int to float
  let mut type_cast = (a_int as f64);
  

let orginal: char = 'I';
  // char to int => 73
  let type_casted: i64 = orginal as i64;
  

To perform type-casting in Rust one must use the as keyword.

let mut foo = 4;
  let mut borrowed_foo = &foo;
  println!("{borrowed_foo}");
  

let mut bar = 3;
  let mut mutable_borrowed_bar = &mut bar;
  println!("{mutable_borrowed_bar}");
  

Here borrowed value borrows the value from value one using & operator.

let mut borrow = 10;
  let deref = &mut borrow;
  
  println!("{}", *deref);
  

De-referencing in rust can be done using the * operator

{
    // The scope limited to this braces
    let a_number = 1;
  }
  println!("{a_number}");
  

This will produce error as the scope of the variable a_number ends at the braces