chapter 4 done

ownership/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "ownership"
+version = "0.1.0"

ownership/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "ownership"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

ownership/src/main.rs

@@ -0,0 +1,44 @@
+fn main() {
+    let s = String::from("hello");
+    takes_ownership(s);
+    let x = 5;
+    makes_copy(x);
+
+    let s1 = gives_ownership();
+    println!("{s1}");
+    let s2 = String::from("Hello");
+    println!("{s2}");
+    let mut s3 = takes_and_gives_back(s2);
+    println!("{s3}");
+    let len = calculate_length(&s3);
+    println!("{s3} -> {len}");
+    change(&mut s3);
+    println!("{s3}");
+
+
+
+}
+fn change(some_string: &mut String){
+    some_string.push_str(", world");
+}
+
+fn takes_ownership(some_string: String) {
+    println!("{some_string}");
+}
+
+fn makes_copy(some_integer: i32) {
+    println!("{some_integer}");
+}
+
+fn gives_ownership() -> String {
+    let some_string = String::from("yours");
+    some_string
+}
+
+fn takes_and_gives_back(a_string: String) -> String {
+    a_string
+}
+
+fn calculate_length(s: &String) -> usize {
+    s.len()
+}

slices/src/main.rs

@@ -1,27 +1,32 @@
 fn main() {
-    let words = String::from("all string of words");
+    let my_string = String::from("Hello world");
-    println!("{words}");
+
-    let first = find_first(&words);
+    let word = find_first(&my_string[0..6]);
-    println!("{first}");
+    println!("{word}");
+
+    let word = find_first(&my_string[..]);
+    println!("{word}");
+
+    let word = find_first(&my_string);
+
+    println!("{word}");
+
+    let my_literal_string = "hello world";
+
+    let word = find_first(&my_literal_string[0..6]);
+    println!("{word}");
+
+    let word = find_first(&my_literal_string[..]);
+    println!("{word}");
+
+    let word = find_first(&my_literal_string);
+
+    println!("{word}");
 
-    let second = find_first2(&words);
-    println!("{second}");
 }
 
 
-fn find_first(words: &String) -> String {
+fn find_first(words: &str) -> &str {
-    let mut word = String::from("");
-    for letter in words.chars() {
-        if letter == ' ' {
-            break;
-        }
-        word.push_str(&letter.to_string());
-    }
-    word
-}
-
-
-fn find_first2(words: &str) -> &str {
     let bytes = words.as_bytes();
 
     for (i, &item) in bytes.iter().enumerate() {