From 1eb1add888b1514fbe802ce2ab7edf720ab107af Mon Sep 17 00:00:00 2001
From: Fabian Schmidt <fabschmidt96@gmail.com>
Date: Wed, 5 Mar 2025 19:44:46 +0100
Subject: [PATCH] Why have I never comitted this?

---
 src/bin/interior_mutability.rs        | 55 +++++++++++++++++++++++++++
 src/bin/move.rs                       | 19 +++++++++
 src/bin/thread_interior_mutability.rs | 50 ++++++++++++++++++++++++
 3 files changed, 124 insertions(+)
 create mode 100644 src/bin/interior_mutability.rs
 create mode 100644 src/bin/move.rs
 create mode 100644 src/bin/thread_interior_mutability.rs

diff --git a/src/bin/interior_mutability.rs b/src/bin/interior_mutability.rs
new file mode 100644
index 0000000..e393534
--- /dev/null
+++ b/src/bin/interior_mutability.rs
@@ -0,0 +1,55 @@
+// https://www.youtube.com/watch?v=HwupNf9iCJk
+
+use std::cell::{Cell, RefCell};
+
+#[derive(Debug)]
+// Could simplify this with Rc (see thread safe example)
+struct Node<'a> {
+    // Cell for copyable values
+    val: Cell<i32>,
+    // RefCell probably better as there is no copying but can panic
+    str_val: RefCell<String>,
+    adjacent: Vec<&'a Node<'a>>,
+}
+
+fn add_one(node: &Node) {
+    let curr_val = node.val.get();
+    node.val.set(curr_val + 1);
+    for adj in node.adjacent.iter() {
+        add_one(adj);
+    }
+}
+
+fn add_urgency(node: &Node) {
+    node.str_val.borrow_mut().push('!');
+    for adj in node.adjacent.iter() {
+        add_urgency(adj);
+    }
+}
+
+fn main() {
+    let a = Node {
+        val: Cell::new(1),
+        str_val: RefCell::new(String::from("aaa")),
+        adjacent: vec![],
+    };
+
+    let b = Node {
+        val: Cell::new(2),
+        str_val: RefCell::new(String::from("bbb")),
+        adjacent: vec![&a],
+    };
+
+    let c = Node {
+        val: Cell::new(4),
+        str_val: RefCell::new(String::from("ccc")),
+        adjacent: vec![&a],
+    };
+    dbg!(&a);
+    dbg!(&b);
+    dbg!(&c);
+    add_one(&b);
+    dbg!(&b);
+    add_urgency(&c);
+    dbg!(&c);
+}
diff --git a/src/bin/move.rs b/src/bin/move.rs
new file mode 100644
index 0000000..abbc838
--- /dev/null
+++ b/src/bin/move.rs
@@ -0,0 +1,19 @@
+// https://www.youtube.com/watch?v=MDvImhzrWr4
+
+fn c<F: FnOnce() + 'static>(f: F) {
+    f();
+}
+
+fn main() {
+    let mut v = vec![1, 2, 3];
+
+    // use move keyword to get around 'static lifetime issue
+    c(move || {
+        v.push(4);
+    }); // without 'static closure lifetime ends here and we have no borrow issue
+
+    // cannot use v after moving the value
+    // this is where rc and refcell come into play
+    //v.push(5);
+    //dbg!(v);
+}
diff --git a/src/bin/thread_interior_mutability.rs b/src/bin/thread_interior_mutability.rs
new file mode 100644
index 0000000..e1af26e
--- /dev/null
+++ b/src/bin/thread_interior_mutability.rs
@@ -0,0 +1,50 @@
+// https://www.youtube.com/watch?v=HwupNf9iCJk
+
+use std::{
+    sync::{Arc, RwLock},
+    thread,
+};
+
+#[derive(Debug)]
+struct Node {
+    // RwLock similar to RefCell but thread safe,
+    // can also use Mutex and then .lock() it instead of calling .read() or .write()
+    str_val: RwLock<String>,
+    adjacent: Vec<Arc<Node>>,
+}
+
+fn add_urgency(node: Arc<Node>) {
+    {
+        node.str_val.write().unwrap().push('!');
+    }
+    for adj in node.adjacent.iter() {
+        add_urgency(adj.clone());
+    }
+}
+
+fn main() {
+    let a = Arc::new(Node {
+        str_val: RwLock::new(String::from("aaa")),
+        adjacent: vec![],
+    });
+
+    let b = Arc::new(Node {
+        str_val: RwLock::new(String::from("bbb")),
+        adjacent: vec![a.clone()],
+    });
+
+    let c = Arc::new(Node {
+        str_val: RwLock::new(String::from("ccc")),
+        adjacent: vec![a.clone()],
+    });
+
+    dbg!(a.clone());
+    dbg!(b.clone());
+    dbg!(c.clone());
+    let t1_b = b.clone();
+    let _t1 = thread::spawn(move || add_urgency(t1_b)).join();
+    dbg!(c.clone());
+    let t2_c = c.clone();
+    let _t2 = thread::spawn(move || add_urgency(t2_c)).join();
+    dbg!(c.clone());
+}