公共枚举的变量都是默认公共的

Vector用的比较多，所以有预导入prelude机制，而hashmap用的比较少，不在prelude中

hashmap 堆内存，同构造

collect特定类型

hashmap/迭代

还是要多写代码，多写代码才能学好编程

panic! 打印错误信息，展开和清理调用栈，并中止执行，默认情况下，展开调用栈。（工作量大）

可以把默认展开改为中止

[profile.release] 生产环境

panice ="abort"

result 枚举：  Ok Err

use std::collections::HashMap;

fn main() {

    println!("Hello, world!");

    let s1 = String::from(" eth is good");

    let s2 = String::from(" eth will up to 10000");

    println!("{}{}", s1, s2);

    let s3 = s1 + &s2;

    println!("{}", s3);

    println!("{}", s2);

    //println!("{}", s1);

    let s4 = String::from(" realms is good");

    let s5 = String::from(" realms will up to 10000");

    let s = format!("{}--{}", s4, s5);

    println!("{}", s);

    let  tokens:Vec<String> = vec![String::from("BTC"),String::from("ETH"),String::from("APX")];

    let  amounts:Vec<f64> = vec![0.0012,1200000.345,167098.1];

    let holdings: HashMap<&String,&f64> = tokens.iter().zip(amounts.iter()).collect();

    println!("{:?}",holdings);

    let mut another_hold = HashMap::new();//必须为mut关键词修饰的，不然不能插入

    another_hold.insert(String::from("SSV"),12345.67);

    println!("{:?}",another_hold);//{:?} 完整输出

    let mut layer2_tvl:HashMap<String,f64> = HashMap::new();

    layer2_tvl.insert(String::from("ARB"),30.15);

    layer2_tvl.insert(String::from("OP"),20.14);//

    layer2_tvl.insert(String::from("OP"),18.14);//同样的key 会覆盖原来的value

    let op_tvl = layer2_tvl.get("OP");

    match op_tvl {

        Some(tvl) => println!("OP TVL is {}",tvl),

        None => println!("OP TVL is not found"),

    }

    layer2_tvl.entry(String::from("STARK")).or_insert(3.105);

    for (layer2,tvl) in &layer2_tvl {

        println!("{}:{}",layer2,tvl);

    }

    let v1 = vec![1,2,3];

    println!("{}",&v1[5]);

    panic!("crash and burn");

    layer2_tvl.entry(String::from("STARK")).or_insert(13.105);

    let stark_tvl = layer2_tvl.get("STARK");

    match stark_tvl {

        Some(tvl) => println!("STARK TVL is {}",tvl),

        None => println!("STARK TVL is not found"),

    }

}