Add copy vs move types

src/add-one-lib/src/lib.rs

@@ -6,8 +6,7 @@
 //
 // Sol:
 // Until this issue is solved https://github.com/rust-lang/cargo/issues/8379,
-// using this small hack: 
-// 
+// using this small hack:
 // Make some test modules available for "use-foo" feature
 // #usefoo - enable this line when this feature is enabled 
 //           (can be enabled by client's Cargo.toml or compiler flag)

src/copy_vs_move.rs

@@ -0,0 +1,32 @@
+#[test]
+fn ex1_ww() {
+    // a. copy
+    let x = 5;
+    let y = x; // !! copied, not moved
+    println!("x: {}!", x);
+        // Ok: Since because integers are simple values with a known, 
+        // fixed size, and these two 5 values are pushed onto the stack
+
+    // b. move
+    let s1 = String::from("hello");
+    let s2 = s1; // !! s1 moved to s2, s1 is invalid at this point
+    // println!("s1: {}!", s1);
+        // error[E0382]: borrow of moved value: `s1`
+        //   --> src/main.rs:15:25
+        //   |
+        // 12 |     let s1 = String::from("hello");
+        //   |         -- move occurs because `s1` has type `String`, 
+        // which does not implement the `Copy` trait
+        // 13 |     let s2 = s1;
+        //   |              -- value moved here
+        // 14 |
+        // 15 |     println!("s1: {}!", s1);
+        //   |                         ^^ value borrowed here after move
+        //   |
+        // help: consider cloning the value if the performance cost is acceptable
+        //   |
+        // 13 |     let s2 = s1.clone();
+        //   |                ++++++++
+
+    assert_eq!(32, 32);
+}

src/lib.rs

@@ -8,6 +8,7 @@
 mod async_;
 mod averaged_collection;
 mod cfg;
+mod copy_vs_move;
 mod ctor_chain;
 mod compile_vs_runtime_read_env_and_file;
 mod concurrency;

src/temp.rs

@@ -1,6 +1,6 @@
 // Template - copy and change this:
 //
-// #[test] 
+// #[test]
 // fn ex1_ww() {
-//     assert_eq!(32,32);
+//     assert_eq!(32, 32);
 // }

src/traits_default_type_parameter.rs

@@ -1,16 +1,16 @@
 use std::ops::Add;
 
-// Original Add trait from std
-pub trait Add_<Rhs = Self> { // <Rhs = Self>: default type parameter
-    type Output;
-    fn add(self, rhs: Rhs) -> Self::Output;
-}
-
 // 1.a. Using "default type parameter"
 // Implementing the Add trait to overload the + operator for Point instances
 #[derive(Debug, PartialEq)]
 struct Point { x: i32, y: i32 }
 
+// For info: Add trait from std
+pub trait Add_<Rhs = Self> { // <Rhs = Self>: default type parameter
+    type Output;
+    fn add(self, rhs: Rhs) -> Self::Output;
+}
+
 impl Add for Point {
     type Output = Point;
 
@@ -30,9 +30,17 @@ impl Add for Point {
 }
 
 // 1.b. Overriding "default type parameter" also newtype pattern
+// https://doc.rust-lang.org/book/ch19-03-advanced-traits.html#default-generic-type-parameters-and-operator-overloading
+
 #[derive(Debug, PartialEq)] struct Millimeters(u32);
 #[derive(Debug, PartialEq)] struct Meters(u32);
 
+// For info: Add trait from std
+trait Add__<Rhs=Self> {
+    type Output;
+    fn add(self, rhs: Rhs) -> Self::Output;
+}
+
 impl Add<Meters> for Millimeters {
     type Output = Millimeters;
     fn add(self, other: Meters) -> Millimeters {