rust_book_code 0.2.1

use std::fmt::Display;

pub fn lifetimes_syntax() {
    let string1 = String::from("abcd");
    let string2 = "xyz";

    let result = longest(string1.as_str(), string2);
    println!("The longest string is: {}", result);

    let string1 = String::from("long string is long");
    let result;
    {
        let string2 = String::from("xyz");
        result = longest(string1.as_str(), string2.as_str());
        println!("The longest string is {}", result);
    }

    // the lifetime of the reference returned by the longest function is the
    // same as the smaller of the lifetimes of the references passed in
    // println!("The longest string is {}", result);
}

fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
    if x.len() > y.len() {
        x
    } else {
        y
    }
}

struct ImportantExcerpt<'a> {
    part: &'a str,
}

impl<'a> ImportantExcerpt<'a> {
    fn level(&self) -> i32 {
        3
    }
}

impl<'a> ImportantExcerpt<'a> {
    fn announce_and_return_part(&self, announcement: &str) -> &str {
        println!("Attention please: {}", announcement);
        self.part
    }
}

pub fn lifetimes_struct() {
    let novel = String::from("Call me Ishmael. Some years ago...");
    let first_sentence = novel.split('.').next().expect("Could not find a '.'");
    let i = ImportantExcerpt {
        part: first_sentence,
    };

    let level = i.level();
    println!("{}", level);
    let announcement = "an announcement";
    let part = i.announce_and_return_part(announcement);
    println!("{}", part);
}

pub fn lifetimes_static() {
    let s: &'static str = "I have a static lifetime.";
    println!("{}", s);
}

pub fn combination() {
    fn longest_with_an_announcement<'a, T>(x: &'a str, y: &'a str, ann: T) -> &'a str
    where
        T: Display,
    {
        println!("Announcement! {}", ann);
        if x.len() > y.len() {
            x
        } else {
            y
        }
    }
}