Add cargo workspace example

Author: shuliang

README.org

@@ -61,4 +61,5 @@ The official [[https://github.com/tokio-rs/tokio][Tokio]] (asynchronous runtime
 The official rust book - [[https://github.com/rust-lang/book][The Rust Programming Language]].
 
 - [[file:the-book/minigrep/src/main.rs][chapter 12: building a command line program]]
+- [[file:the-book/add/adder/src/main.rs][chapter 14.3: cargo workspaces]]
 - [[file:the-book/hello/src/bin/main.rs][chapter 20: building a multithreaded web server]]

the-book/add/Cargo.lock

@@ -0,0 +1,6 @@
+[workspace]
+
+members = [
+    "adder",
+    "add_one",
+]

the-book/add/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "add_one"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+rand = "0.8.5"

the-book/add/add_one/Cargo.toml

@@ -0,0 +1,25 @@
+// use rand;
+
+pub fn add(left: usize, right: usize) -> usize {
+    left + right
+}
+
+pub fn add_one(x: i32) -> i32 {
+    x + 1
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn it_works() {
+        let result = add(2, 2);
+        assert_eq!(result, 4);
+    }
+
+    #[test]
+    fn test_add_one() {
+        assert_eq!(add_one(5), 6);
+    }
+}

the-book/add/add_one/src/lib.rs

@@ -0,0 +1,10 @@
+[package]
+name = "adder"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+add_one = { path = "../add_one" }
+rand = "0.8.5"

the-book/add/adder/Cargo.toml

@@ -0,0 +1,10 @@
+use add_one;
+use rand::prelude::*;
+
+fn main() {
+    let num = 10;
+    println!("Hello, world! {num} plus one is {}!", add_one::add_one(num));
+    let mut rng = rand::thread_rng();
+    let y: f64 = rng.gen();
+    println!("random: {y}");
+}