Rust learning: lessons, notes, and exercise crates

ownership/.gitignore

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+/target

ownership/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "ownership"
+version = "0.1.0"

ownership/Cargo.toml

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+[package]
+name = "ownership"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]

ownership/src/main.rs

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+fn main() {
+    let mut s = String::from("hello");
+    s.push_str(", world");
+
+    let x = calculate_length(&s);
+
+    println!("{s} with len {x}");
+
+    let y = "lksadjflksajdfc";
+    println!("{y}");
+
+    // {
+    //     let x = 12;
+    // }
+    // println!("{x}");
+
+    {
+        let s1 = String::from("hello");
+        let s2 = s1;
+
+        println!("{s2}, world!");
+    }
+
+    let s = String::from("hello"); // s comes into scope
+
+    takes_ownership(s); // s's value moves into the function...
+    // ... and so is no longer valid here
+
+    let x = 5; // x comes into scope
+
+    makes_copy(x); // Because i32 implements the Copy trait,
+    // x does NOT move into the function,
+    // so it's okay to use x afterward.
+
+    let mut s = String::from("hello");
+
+    {
+        let r1 = &mut s;
+        println!("{r1}");
+        let x = r1.len();
+        println!("{x}");
+    } // r1 goes out of scope here, so we can make a new reference with no problems.
+
+    let r2 = &mut s;
+}
+
+fn takes_ownership(some_string: String) {
+    // some_string comes into scope
+    println!("{some_string}");
+} // Here, some_string goes out of scope and `drop` is called. The backing
+// memory is freed.
+
+fn makes_copy(some_integer: i32) {
+    // some_integer comes into scope
+    println!("{some_integer}");
+} // Here, some_integer goes out of scope. Nothing special happens.
+
+fn calculate_length(s: &String) -> usize {
+    s.len()
+}
+
+fn first_word(s: &String) -> usize {
+    let bytes = s.as_bytes();
+
+    for (i, &item) in bytes.iter().enumerate() {
+        if item == b' ' {
+            return i;
+        }
+    }
+    s.len()
+}