result-panic/panic

[giscus[bot]]

result-panic/panic

Learning Rust By Practice, narrowing the gap between beginner and skilled-dev with challenging examples, exercises and projects.

https://zh.practice.rs/result-panic/panic.html

[zmh1994]

第2题的没有答案呀，答案复制的原题

[ZLD1819858]

speed和cph都是u8类型的，221*2溢出了。可以把221调整小，或者上面另外一个朋友的做法，将这俩变量先转换成f64再做运算

[tjw123hh]

// 修复所有的 panic，让代码工作
fn main() {
    assert_eq!("abc".as_bytes(), [97, 98, 99]);

    let _v = vec![1, 2, 3];
    let _ele = _v[2];
    let _ele = _v.get(2).unwrap();

    // 大部分时候编译器是可以帮我们提前发现溢出错误，并阻止编译通过。但是也有一些时候，这种溢出问题直到运行期才会出现
    let _v = production_rate_per_hour(2);

    divide(15.0, 0.0);

    println!("Success!")
}

fn divide(x:f64, y:f64) {
    println!("{}", x / y)
}

fn production_rate_per_hour(speed: u32) -> f64 {
    let cph: u32 = 221;
    match speed {
        1..=4 => (speed * cph) as f64,
        5..=8 => (speed * cph) as f64 * 0.9,
        9..=10 => (speed * cph) as f64 * 0.77,
        _ => 0 as f64,
    }
}

pub fn working_items_per_minute(speed: u32) -> u32 {
    (production_rate_per_hour(speed) / 60 as f64) as u32
}

[tjw123hh]

或者用#[allow(unused_variables)]
v应该不用改成_v

[Yestercafe]

#[allow(unused_variables)]
fn main() {
    assert_eq!("abc".as_bytes(), [97, 98, 99]);

    let v = vec![1, 2, 3, 4];
    let ele = v[3];
    // unwrap may panic when get return a None
    let ele = v.get(3).unwrap();

    // Sometimes, the compiler is unable to find the overflow errors for you in compile time ,so a panic will occur
    let v = production_rate_per_hour(2);

    // because of the same reason as above, we have to wrap it in a function to make the panic occur
    divide(15, 1)
}

fn divide(x:u8, y:u8) {
    println!("{}", x / y)
}

fn production_rate_per_hour(speed: u8) -> f64 {
    let cph: u8 = 221;
    match speed {
        1..=4 => speed as f64 * cph as f64,
        5..=8 => speed as f64 * cph as f64 * 0.9,
        9..=10 => speed as f64 * cph as f64 * 0.77,
        _ => 0 as f64,
    }
}

pub fn working_items_per_minute(speed: u8) -> u32 {
    (production_rate_per_hour(speed) / 60 as f64) as u32
}

$ RUST_BACKTRACE= cargo run

[DaZhou-ECHO]

第三题不能有空格吧，$RUST_BACKTRACE= cargo run

[jingth]

/*
// 填空
fn drink(beverage: &str) {
if beverage == "lemonade" {
println!("Success!");
// 实现下面的代码
panic!("crash down.");
}

println!("Exercise Failed if printing out this line!");

}

fn main() {
drink("lemonade");

println!("Exercise Failed if printing out this line!");

}
*/

// 修复所有的 panic，让代码工作
fn main() {
assert_eq!("abc".as_bytes(), [97, 98, 99]);

let mut v = vec![1., 2., 3., 4.];
let ele = v[3];
let ele = v.get(3).unwrap();

// 大部分时候编译器是可以帮我们提前发现溢出错误，并阻止编译通过。但是也有一些时候，这种溢出问题直到运行期才会出现
let v = production_rate_per_hour(2);

divide(15, 1);

println!("Success!")

}

fn divide(x:u8, y:u8) {
println!("{}", x / y)
}

fn production_rate_per_hour(speed: u16) -> f64 {
let cph: u16 = 221;
match speed {
1..=4 => (speed * cph) as f64,
5..=8 => (speed * cph) as f64 * 0.9,
9..=10 => (speed * cph) as f64 * 0.77,
_ => 0 as f64,
}
}

pub fn working_items_per_minute(speed: u16) -> u32 {
(production_rate_per_hour(speed) / 60 as f64) as u32
}

/*

填空以打印全部的调用栈

提示: 你可以在之前的默认 panic 信息中找到相关线索

$ $env:RUST_BACKTRACE=1 ; cargo run
thread 'main' panicked at 'assertion failed: (left == right)
left: [97, 98, 99],
right: [96, 97, 98]', src/main.rs:3:5
stack backtrace:
0: rust_begin_unwind
at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/std/src/panicking.rs:498:5
1: core::panicking::panic_fmt
at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/panicking.rs:116:14
2: core::panicking::assert_failed_inner
3: core::panicking::assert_failed
at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/panicking.rs:154:5
4: study_cargo::main
at ./src/main.rs:3:5
5: core::ops::function::FnOnce::call_once
at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/ops/function.rs:227:5
note: Some details are omitted, run with RUST_BACKTRACE=full for a verbose backtrace.
*/

[ZLD1819858]

还是Linux下展开栈回溯信息的命令好记：
BACKTRACK=1 cargo run
win下：$end:BACKTRACE=1; cargo run

[tjw123hh]

BACKTRACK->BACKTRACE

[tjw123hh]

前面还要加RUST_

[tabris233]

// 修复所有的 panic，让代码工作
fn main() {
    assert_eq!("abc".as_bytes(), [97, 98, 99]);

    let v = vec![1, 2, 3];
    let _ele = v[2];
    let _ele = v.get(2).unwrap();

    // 大部分时候编译器是可以帮我们提前发现溢出错误，并阻止编译通过。但是也有一些时候，这种溢出问题直到运行期才会出现
    let _v = production_rate_per_hour(0);

    divide(15, 1);

    println!("Success!")
}

fn divide(x:u8, y:u8) {
    println!("{}", x / y)
}

fn production_rate_per_hour(speed: u8) -> f64 {
    let cph: u8 = 221;
    match speed {
        1..=4 => (speed * cph) as f64,
        5..=8 => (speed * cph) as f64 * 0.9,
        9..=10 => (speed * cph) as f64 * 0.77,
        _ => 0 as f64,
    }
}

pub fn working_items_per_minute(speed: u8) -> u32 {
    (production_rate_per_hour(speed) / 60 as f64) as u32
}

RUST_BACKTRACE=1 cargo run

[Bruce012356]

mark

[XU0618]

lala

[Ghy0202]

1、终止了main线程

// 填空
fn drink(beverage: &str) {
    if beverage == "lemonade" {
        println!("Success!");
        // 实现下面的代码
        panic!("error");
     }

    println!("Exercise Failed if printing out this line!");
}

fn main() {
    drink("lemonade");

    println!("Exercise Failed if printing out this line!");
}

2、就是修复bug

// 修复所有的 panic，让代码工作
fn main() {
    assert_eq!("abc".as_bytes(), [97, 98, 99]);

    let v = vec![1, 2, 3,4];
    let _ele = v[3];
    let _ele = v.get(3).unwrap();

    // 大部分时候编译器是可以帮我们提前发现溢出错误，并阻止编译通过。但是也有一些时候，这种溢出问题直到运行期才会出现
    let _v = production_rate_per_hour(2);

    divide(15, 0);

    println!("Success!")
}

fn divide(x:u8, y:u8) {
    if y!=0{
        println!("{}", x / y)
    }
}

fn production_rate_per_hour(speed: u8) -> f64 {
    let cph: i32 = 221;
    match speed {
        1..=4 => ((speed as i32) * cph) as f64,
        5..=8 => ((speed as i32) * cph) as f64 * 0.9,
        9..=10 => ((speed as i32) * cph) as f64 * 0.77,
        _ => 0 as f64,
    }
}

pub fn working_items_per_minute(speed: u8) -> f64 {
    (production_rate_per_hour(speed) / 60 as f64) as f64
}

[tjw123hh]

类Unix（Bash）：

RUST_BACKTRACE=1 cargo run

Windows：（没有语法高亮加个>好了）

> $env:RUST_BACKTRACE=1 ; cargo run

[chenhai998]

done

[DylanJinx]

done~~~