Smart Pointers and Advanced Patterns

src/day31_to_day33/advanced_patterns.rs

@@ -0,0 +1,53 @@
+pub fn run() {
+    println!("\nAdvanced Pattern Matching Examples:");
+
+    // Example 1: Pattern matching with guards
+    pattern_guards();
+
+    // Example 2: Multiple patterns
+    multiple_patterns();
+
+    // Example 3: Destructuring
+    destructuring_examples();
+}
+
+fn pattern_guards() {
+    let number = 4;
+
+    match number {
+        n @ 1..=5 if n % 2 == 0 => println!("{} is even and between 1 and 5", n),
+        n @ 1..=5 => println!("{} is odd and between 1 and 5", n),
+        n if n % 2 == 0 => println!("{} is even", n),
+        _ => println!("Doesn't match any pattern"),
+    }
+}
+
+fn multiple_patterns() {
+    let x = 1;
+    match x {
+        1 | 2 | 3 => println!("One, two, or three"),
+        4..=10 => println!("Four through ten"),
+        _ => println!("Something else"),
+    }
+}
+
+fn destructuring_examples() {
+    // Tuple destructuring
+    let point = (3, -7);
+    let (x, y) = point;
+    println!("Point: x = {}, y = {}", x, y);
+
+    // Struct destructuring
+    struct Person {
+        name: String,
+        age: u32,
+    }
+
+    let person = Person {
+        name: String::from("Alice"),
+        age: 30,
+    };
+
+    let Person { name, age } = person;
+    println!("{} is {} years old", name, age);
+} 

src/day31_to_day33/box_pointer.rs

@@ -0,0 +1,28 @@
+use std::mem;
+
+// Example of recursive type using Box
+#[derive(Debug)]
+enum List<T> {
+    Cons(T, Box<List<T>>),
+    Nil,
+}
+
+pub fn run() {
+    println!("\nBox Smart Pointer Examples:");
+
+    // Example 1: Using Box for heap allocation
+    let b = Box::new(5);
+    println!("Box contains: {}", b);
+
+    // Example 2: Recursive type with Box
+    let list = List::Cons(1, Box::new(List::Cons(2, Box::new(List::Nil))));
+    println!("List: {:?}", list);
+
+    // Example 3: Large data on heap
+    let large_data = Box::new([0; 1000]);
+    println!("Large array size: {} bytes", mem::size_of_val(&*large_data));
+
+    // Example 4: Box for trait objects
+    let trait_object: Box<dyn ToString> = Box::new(42);
+    println!("Trait object to string: {}", trait_object.to_string());
+} 

src/day31_to_day33/custom_smart_pointer.rs

@@ -0,0 +1,43 @@
+use std::ops::Deref;
+use std::ops::DerefMut;
+
+// Custom smart pointer
+struct MyBox<T>(T);
+
+impl<T> MyBox<T> {
+    fn new(x: T) -> MyBox<T> {
+        MyBox(x)
+    }
+}
+
+// Implementing Deref
+impl<T> Deref for MyBox<T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+// Implementing DerefMut
+impl<T> DerefMut for MyBox<T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}
+
+pub fn run() {
+    println!("\nCustom Smart Pointer Examples:");
+
+    // Using our custom smart pointer
+    let x = 5;
+    let y = MyBox::new(x);
+
+    println!("Original value: {}", x);
+    println!("Value through MyBox: {}", *y);
+
+    // Using with mutable reference
+    let mut z = MyBox::new(String::from("Hello"));
+    z.push_str(" World!");
+    println!("Mutable MyBox: {}", *z);
+} 

src/day31_to_day33/mod.rs

@@ -0,0 +1,16 @@
+pub mod box_pointer;
+pub mod rc_pointer;
+pub mod ref_cell;
+pub mod weak_references;
+pub mod advanced_patterns;
+pub mod custom_smart_pointer;
+
+pub fn run() {
+    println!("Days 31-33: Smart Pointers and Advanced Patterns");
+    box_pointer::run();
+    rc_pointer::run();
+    ref_cell::run();
+    weak_references::run();
+    advanced_patterns::run();
+    custom_smart_pointer::run();
+}

src/day31_to_day33/rc_pointer.rs

@@ -0,0 +1,36 @@
+use std::rc::Rc;
+
+#[derive(Debug)]
+struct Node {
+    value: i32,
+    next: Option<Rc<Node>>,
+}
+
+pub fn run() {
+    println!("\nRc Smart Pointer Examples:");
+
+    // Example 1: Basic Rc usage
+    let value = Rc::new(42);
+    let value2 = Rc::clone(&value);
+    println!("Reference count: {}", Rc::strong_count(&value));
+    println!("Values: {} {}", value, value2);
+
+    // Example 2: Shared ownership in a list
+    let node3 = Rc::new(Node {
+        value: 3,
+        next: None,
+    });
+
+    let node2 = Rc::new(Node {
+        value: 2,
+        next: Some(Rc::clone(&node3)),
+    });
+
+    let node1 = Node {
+        value: 1,
+        next: Some(Rc::clone(&node2)),
+    };
+
+    println!("Node 1: {:?}", node1);
+    println!("Reference count of node2: {}", Rc::strong_count(&node2));
+} 

src/day31_to_day33/ref_cell.rs

@@ -0,0 +1,27 @@
+use std::cell::RefCell;
+
+pub fn run() {
+    println!("\nRefCell Examples:");
+
+    // Example 1: Basic RefCell usage
+    let data = RefCell::new(42);
+    println!("Initial value: {:?}", data);
+
+    // Mutate through RefCell
+    *data.borrow_mut() = 100;
+    println!("After mutation: {:?}", data);
+
+    // Example 2: Multiple borrows
+    {
+        let reading = data.borrow();
+        println!("First borrow: {}", *reading);
+
+        // This would panic - uncomment to see:
+        // let writing = data.borrow_mut(); // Already borrowed
+    }
+
+    // Example 3: RefCell with a more complex type
+    let list = RefCell::new(vec![1, 2, 3]);
+    list.borrow_mut().push(4);
+    println!("Vector: {:?}", list.borrow());
+} 

src/day31_to_day33/weak_references.rs

@@ -0,0 +1,34 @@
+use std::rc::{Rc, Weak};
+use std::cell::RefCell;
+
+#[derive(Debug)]
+struct Node {
+    value: i32,
+    parent: RefCell<Weak<Node>>,
+    children: RefCell<Vec<Rc<Node>>>,
+}
+
+pub fn run() {
+    println!("\nWeak Reference Examples:");
+
+    // Create a tree structure with weak parent references
+    let leaf = Rc::new(Node {
+        value: 3,
+        parent: RefCell::new(Weak::new()),
+        children: RefCell::new(vec![]),
+    });
+
+    println!("Leaf parent = {:?}", leaf.parent.borrow().upgrade());
+
+    let branch = Rc::new(Node {
+        value: 5,
+        parent: RefCell::new(Weak::new()),
+        children: RefCell::new(vec![Rc::clone(&leaf)]),
+    });
+
+    *leaf.parent.borrow_mut() = Rc::downgrade(&branch);
+
+    println!("Leaf parent = {:?}", leaf.parent.borrow().upgrade());
+    println!("Branch strong count = {}", Rc::strong_count(&branch));
+    println!("Branch weak count = {}", Rc::weak_count(&branch));
+} 

src/main.rs

@@ -28,6 +28,9 @@ pub mod day25_to_day27;
 //Day 28 to day 30
 pub mod day28_to_day30;
 
+//Day 31 to day 33
+pub mod day31_to_day33;
+
 fn main() {
     // day01_to_day03::run();
     // day04_to_day06::run();
@@ -38,6 +41,7 @@ fn main() {
     // day19_to_day21::run();
     // day22_to_day24::run();
     // day25_to_day27::run();
-    day28_to_day30::run();
+    // day28_to_day30::run();
+    day31_to_day33::run();
 
 }