did modulule chapter.

the_book/restaurant/Cargo.toml

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

the_book/restaurant/src/front_of_house.rs

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+pub mod hosting;

the_book/restaurant/src/front_of_house/hosting.rs

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+pub fn add_to_waitlist() {}

the_book/restaurant/src/lib.rs

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+#[cfg(test)]
+mod tests {
+    #[test]
+    fn it_works() {
+        let result = 2 + 2;
+        assert_eq!(result, 4);
+    }
+}
+mod front_of_house;
+
+pub use crate::front_of_house::hosting;
+
+pub fn eat_at_restaurant() {
+    hosting::add_to_waitlist();
+}