Rust模块关键词和哈希表详解

mod front_of_house {
    pub mod hosting {
        //这里的pub是让这个模块公有化，也就是说可以通过 crate::front_of_house::hosting::访问模块中的元素
        pub fn add_to_waitlist() {}//但是模块内部的元素是否公有化仍然是需要pub关键字指明的，并且我们知道这样是合理的，因为这样我们对模块内部的元素哪些需要公开，哪些需要私有有更精准的把控。
    }
}
pub fn eat_at_restaurant() {
    // 绝对路径
    crate::front_of_house::hosting::add_to_waitlist();
    // 相对路径
    front_of_house::hosting::add_to_waitlist();
}

fn deliver_order() {}
mod back_of_house {
    fn fix_incorrect_order() {
        cook_order();
        super::deliver_order();
    }
    fn cook_order() {}
}

use std::fmt::Result;
use std::io::Result as IoResult

rand = "0.8.5"

use rand::Rng
fn main() {
    let secret_number = rand::thread_rng().gen_range(1..=100);
}

use std::cmp::Ordering;
use std::io;
//等价于
use std::{cmp::Ordering, io};
use std::io;
use std::io::Write;
//等价于
use std::io::{self, Write};

use std::collections::HashMap;
let mut scores = HashMap::new();
scores.insert(String::from("Blue"), 10);
scores.insert(String::from("Yellow"), 50);

use std::collections::HashMap;
let mut scores = HashMap::new();
scores.insert(String::from("Blue"), 10);
scores.insert(String::from("Yellow"), 50);
let team_name = String::from("Blue");
let score = scores.get(&team_name).copied().unwrap_or(0);

use std::collections::HashMap;
let mut scores = HashMap::new();
scores.insert(String::from("Blue"), 10);
scores.insert(String::from("Yellow"), 50);
for (key, value) in &scores {
    println!("{key}: {value}");
}

use std::collections::HashMap;
let field_name = String::from("Favorite color");
let field_value = String::from("Blue");
let mut map = HashMap::new();
map.insert(field_name, field_value);
// 这里 field_name 和 field_value 不再有效，
// 尝试使用它们看看会出现什么编译错误！

use std::collections::HashMap;
let mut scores = HashMap::new();
scores.insert(String::from("Blue"), 10);
scores.entry(String::from("Yellow")).or_insert(50);
scores.entry(String::from("Blue")).or_insert(50);
println!("{scores:?}");

use std::collections::HashMap;
let text = "hello world wonderful world";
let mut map = HashMap::new();
for word in text.split_whitespace() {
    let count = map.entry(word).or_insert(0);
    *count += 1;
}
println!("{map:?}");