Add traits

book/aggregator/Cargo.toml

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

book/aggregator/src/lib.rs

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+pub trait Summary {
+    fn summarise_author(&self) -> String;
+
+    fn summarise(&self) -> String {
+        format!("(Read more from {}...)", self.summarise_author())
+    }
+}
+
+pub struct NewsArticle {
+    pub headline: String,
+    pub location: String,
+    pub author: String,
+    pub content: String,
+}
+
+impl Summary for NewsArticle {
+    fn summarise_author(&self) -> String {
+        format!("@{}", self.author)
+    }
+    // fn summarise(&self) -> String {
+    //     format!("{}, by {} ({})", self.headline, self.author, self.location)
+    // }
+}
+
+pub struct Tweet {
+    pub username: String,
+    pub content: String,
+    pub reply: bool,
+    pub retweet: bool,
+}
+
+impl Summary for Tweet {
+    fn summarise_author(&self) -> String {
+        format!("@{}", self.username)
+    }
+    //
+    // fn summarise(&self) -> String {
+    //     format!("{}: {}", self.username, self.content)
+    // }
+}
+
+fn returns_summarise() -> impl Summary {
+    Tweet {
+        username: String::from("horse_ebooks"),
+        content: String::from("of course, as you probably already know, people"),
+        reply: false,
+        retweet: false,
+    }
+}

book/aggregator/src/main.rs

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+use aggregator::{NewsArticle, Summary, Tweet};
+
+fn largest<T: PartialOrd + Copy>(list: &[T]) -> T {
+    let mut largest = list[0];
+
+    for &item in list {
+        if item > largest {
+            largest = item;
+        }
+    }
+
+    largest
+}
+
+fn largest_no_copy<T: PartialOrd>(list: &[T]) -> &T {
+    let mut largest = list.get(0).expect("oh no");
+
+    for item in list {
+        if item > largest {
+            largest = item;
+        }
+    }
+
+    largest
+}
+
+fn main() {
+    let tweet = Tweet {
+        username: String::from("horse_ebooks"),
+        content: String::from("of course, as you probably already know, people"),
+        reply: false,
+        retweet: false,
+    };
+
+    println!("1 new tweet: \n\t{}", tweet.summarise());
+
+    let article = NewsArticle {
+        headline: String::from("Penguins win the Stanley Cup Championship!"),
+        location: String::from("Pittsburgh, PA, USA"),
+        author: String::from("Iceburgh"),
+        content: String::from(
+            "The Pittsburgh Penguins once again are the best \
+             hockey team in the NHL.",
+        ),
+    };
+
+    println!("New article available: \n\t{}", article.summarise());
+
+    let number_list = vec![34, 50, 25, 100, 65];
+    let result = largest_no_copy(&number_list);
+    println!("The largest number is {}", result);
+
+    let char_list = vec!['y', 'm', 'a', 'q'];
+    let result = largest_no_copy(&char_list);
+    println!("The largest char is {}", result);
+}