RustDay06------Exercise[81-90]

81.宏函数里面的不同的匹配规则需要使用分号隔开

// macros4.rs
//
// Execute `rustlings hint macros4` or use the `hint` watch subcommand for a
// hint.// I AM NOT DONE#[rustfmt::skip]
macro_rules! my_macro {() => {println!("Check out my macro!");};($val:expr) => {println!("Look at this other macro: {}", $val);};
}fn main() {my_macro!();my_macro!(7777);
}

82.使用内部封装好的宏来替代某些常数

// clippy1.rs
//
// The Clippy tool is a collection of lints to analyze your code so you can
// catch common mistakes and improve your Rust code.
//
// For these exercises the code will fail to compile when there are clippy
// warnings check clippy's suggestions from the output to solve the exercise.
//
// Execute `rustlings hint clippy1` or use the `hint` watch subcommand for a
// hint.// I AM NOT DONEuse std::f32;fn main() {let pi = f32::consts::PI;// 3.14f32;let radius = 5.00f32;let area = pi * f32::powi(radius, 2);println!("The area of a circle with radius {:.2} is {:.5}!",radius, area)
}

83.if let回顾

// clippy2.rs
// 
// Execute `rustlings hint clippy2` or use the `hint` watch subcommand for a
// hint.// I AM  DONEfn main() {let mut res = 42;let option = Some(12);if let Some(x)=option {res += x;}println!("{}", res);
}

84.按照提示修改

这题说明 resize是原地操作 没有返回值

交换值必须要借助中间变量

// clippy3.rs
// 
// Here's a couple more easy Clippy fixes, so you can see its utility.
//
// Execute `rustlings hint clippy3` or use the `hint` watch subcommand for a hint.// I AM NOT DONE#[allow(unused_variables, unused_assignments)]
fn main() {let my_option: Option<()> = None;// if my_option.is_none() {//     my_option.unwrap();// }let my_arr = &[-1, -2, -3,-4, -5, -6,];println!("My array! Here it is: {:?}", my_arr);let my_empty_vec = vec![1, 2, 3, 4, 5];println!("This Vec is empty, see? {:?}", my_empty_vec);let mut value_a = 45;let mut value_b = 66;// Let's swap these two!let mut temp =0;temp=value_a;value_a = value_b;value_b = temp;println!("value a: {}; value b: {}", value_a, value_b);
}

85.使用as强制转换类型

// using_as.rs
//
// Type casting in Rust is done via the usage of the `as` operator. Please note
// that the `as` operator is not only used when type casting. It also helps with
// renaming imports.
//
// The goal is to make sure that the division does not fail to compile and
// returns the proper type.
//
// Execute `rustlings hint using_as` or use the `hint` watch subcommand for a
// hint.// I AM NOT DONEfn average(values: &[f64]) -> f64 {let total = values.iter().sum::<f64>();total / values.len() as f64
}fn main() {let values = [3.5, 0.3, 13.0, 11.7];println!("{}", average(&values));
}#[cfg(test)]
mod tests {use super::*;#[test]fn returns_proper_type_and_value() {assert_eq!(average(&[3.5, 0.3, 13.0, 11.7]), 7.125);}
}

86.大佬的奇特匹配orz

这题看了大佬的写法,太beautiful了(只有9行)

// from_into.rs
//
// The From trait is used for value-to-value conversions. If From is implemented
// correctly for a type, the Into trait should work conversely. You can read
// more about it at https://doc.rust-lang.org/std/convert/trait.From.html
//
// Execute `rustlings hint from_into` or use the `hint` watch subcommand for a
// hint.#[derive(Debug)]
struct Person {name: String,age: usize,
}// We implement the Default trait to use it as a fallback
// when the provided string is not convertible into a Person object
impl Default for Person {fn default() -> Person {Person {name: String::from("John"),age: 30,}}
}// Your task is to complete this implementation in order for the line `let p =
// Person::from("Mark,20")` to compile Please note that you'll need to parse the
// age component into a `usize` with something like `"4".parse::<usize>()`. The
// outcome of this needs to be handled appropriately.
//
// Steps:
// 1. If the length of the provided string is 0, then return the default of
//    Person.
// 2. Split the given string on the commas present in it.
// 3. Extract the first element from the split operation and use it as the name.
// 4. If the name is empty, then return the default of Person.
// 5. Extract the other element from the split operation and parse it into a
//    `usize` as the age.
// If while parsing the age, something goes wrong, then return the default of
// Person Otherwise, then return an instantiated Person object with the results// I AM NOT DONEimpl From<&str> for Person {fn from(s: &str) -> Person {let mut iter=s.trim().split(',');let name=iter.next().unwrap_or_default();let age = iter.next().and_then(|x| x.parse::<usize>().ok()).unwrap_or_default();match (name,age,iter.next().is_some()) {("",_,_) =>Person::default(),(_,0,_) => Person::default(),(_,_,true) =>Person::default(),(name,age,_) =>Person{name:name.to_string(),age},}}
}fn main() {// Use the `from` functionlet p1 = Person::from("Mark,20");// Since From is implemented for Person, we should be able to use Intolet p2: Person = "Gerald,70".into();println!("{:?}", p1);println!("{:?}", p2);
}#[cfg(test)]
mod tests {use super::*;#[test]fn test_default() {// Test that the default person is 30 year old Johnlet dp = Person::default();assert_eq!(dp.name, "John");assert_eq!(dp.age, 30);}#[test]fn test_bad_convert() {// Test that John is returned when bad string is providedlet p = Person::from("");assert_eq!(p.name, "John");assert_eq!(p.age, 30);}#[test]fn test_good_convert() {// Test that "Mark,20" workslet p = Person::from("Mark,20");assert_eq!(p.name, "Mark");assert_eq!(p.age, 20);}#[test]fn test_bad_age() {// Test that "Mark,twenty" will return the default person due to an// error in parsing agelet p = Person::from("Mark,twenty");assert_eq!(p.name, "John");assert_eq!(p.age, 30);}#[test]fn test_missing_comma_and_age() {let p: Person = Person::from("Mark");assert_eq!(p.name, "John");assert_eq!(p.age, 30);}#[test]fn test_missing_age() {let p: Person = Person::from("Mark,");assert_eq!(p.name, "John");assert_eq!(p.age, 30);}#[test]fn test_missing_name() {let p: Person = Person::from(",1");assert_eq!(p.name, "John");assert_eq!(p.age, 30);}#[test]fn test_missing_name_and_age() {let p: Person = Person::from(",");assert_eq!(p.name, "John");assert_eq!(p.age, 30);}#[test]fn test_missing_name_and_invalid_age() {let p: Person = Person::from(",one");assert_eq!(p.name, "John");assert_eq!(p.age, 30);}#[test]fn test_trailing_comma() {let p: Person = Person::from("Mike,32,");assert_eq!(p.name, "John");assert_eq!(p.age, 30);}#[test]fn test_trailing_comma_and_some_string() {let p: Person = Person::from("Mike,32,man");assert_eq!(p.name, "John");assert_eq!(p.age, 30);}
}

下面是我自己的丑陋的写法

// from_into.rs
//
// The From trait is used for value-to-value conversions. If From is implemented
// correctly for a type, the Into trait should work conversely. You can read
// more about it at https://doc.rust-lang.org/std/convert/trait.From.html
//
// Execute `rustlings hint from_into` or use the `hint` watch subcommand for a
// hint.#[derive(Debug)]
struct Person {name: String,age: usize,
}// We implement the Default trait to use it as a fallback
// when the provided string is not convertible into a Person object
impl Default for Person {fn default() -> Person {Person {name: String::from("John"),age: 30,}}
}// Your task is to complete this implementation in order for the line `let p =
// Person::from("Mark,20")` to compile Please note that you'll need to parse the
// age component into a `usize` with something like `"4".parse::<usize>()`. The
// outcome of this needs to be handled appropriately.
//
// Steps:
// 1. If the length of the provided string is 0, then return the default of
//    Person.
// 2. Split the given string on the commas present in it.
// 3. Extract the first element from the split operation and use it as the name.
// 4. If the name is empty, then return the default of Person.
// 5. Extract the other element from the split operation and parse it into a
//    `usize` as the age.
// If while parsing the age, something goes wrong, then return the default of
// Person Otherwise, then return an instantiated Person object with the resultsimpl From<&str> for Person {fn from(s: &str) -> Person {let dataList:Vec<&str> =s.split(',').collect();println!("{:?}",dataList);// 数据量不对if dataList.len() != 2 || dataList[0]=="" || dataList[1]=="" {Person {name: String::from("John"),age: 30,}}else {if  dataList[1].chars().all(|x| x.is_digit(10)) {let uAge:usize = dataList[1].parse().unwrap();Person {name: dataList[0].to_string(),age: uAge,}}//    数据格式不对else {Person {name: String::from("John"),age: 30,}}}}
}fn main() {// Use the `from` functionlet p1 = Person::from("Mark,20");// Since From is implemented for Person, we should be able to use Intolet p2: Person = "Gerald,70".into();println!("{:?}", p1);println!("{:?}", p2);
}#[cfg(test)]
mod tests {use super::*;#[test]fn test_default() {// Test that the default person is 30 year old Johnlet dp = Person::default();assert_eq!(dp.name, "John");assert_eq!(dp.age, 30);}#[test]fn test_bad_convert() {// Test that John is returned when bad string is providedlet p = Person::from("");assert_eq!(p.name, "John");assert_eq!(p.age, 30);}#[test]fn test_good_convert() {// Test that "Mark,20" workslet p = Person::from("Mark,20");assert_eq!(p.name, "Mark");assert_eq!(p.age, 20);}#[test]fn test_bad_age() {// Test that "Mark,twenty" will return the default person due to an// error in parsing agelet p = Person::from("Mark,twenty");assert_eq!(p.name, "John");assert_eq!(p.age, 30);}#[test]fn test_missing_comma_and_age() {let p: Person = Person::from("Mark");assert_eq!(p.name, "John");assert_eq!(p.age, 30);}#[test]fn test_missing_age() {let p: Person = Person::from("Mark,");assert_eq!(p.name, "John");assert_eq!(p.age, 30);}#[test]fn test_missing_name() {let p: Person = Person::from(",1");assert_eq!(p.name, "John");assert_eq!(p.age, 30);}#[test]fn test_missing_name_and_age() {let p: Person = Person::from(",");assert_eq!(p.name, "John");assert_eq!(p.age, 30);}#[test]fn test_missing_name_and_invalid_age() {let p: Person = Person::from(",one");assert_eq!(p.name, "John");assert_eq!(p.age, 30);}#[test]fn test_trailing_comma() {let p: Person = Person::from("Mike,32,");assert_eq!(p.name, "John");assert_eq!(p.age, 30);}#[test]fn test_trailing_comma_and_some_string() {let p: Person = Person::from("Mike,32,man");assert_eq!(p.name, "John");assert_eq!(p.age, 30);}
}

87.对字符串进行合法判断

用我丑陋的写法写模拟orz,这题看看题目意思,知道大概要对字符串处理

正常返回Ok

错误返回错误类型

主要是凭感觉写的,这里面应该是通过系统库FromStr在创建的时候自动调用from_str来进行初始化,返回一个Person对象

// from_str.rs
//
// This is similar to from_into.rs, but this time we'll implement `FromStr` and
// return errors instead of falling back to a default value. Additionally, upon
// implementing FromStr, you can use the `parse` method on strings to generate
// an object of the implementor type. You can read more about it at
// https://doc.rust-lang.org/std/str/trait.FromStr.html
//
// Execute `rustlings hint from_str` or use the `hint` watch subcommand for a
// hint.use std::num::ParseIntError;
use std::str::FromStr;#[derive(Debug, PartialEq)]
struct Person {name: String,age: usize,
}// We will use this error type for the `FromStr` implementation.
#[derive(Debug, PartialEq)]
enum ParsePersonError {// Empty input stringEmpty,// Incorrect number of fieldsBadLen,// Empty name fieldNoName,// Wrapped error from parse::<usize>()ParseInt(ParseIntError),
}// I AM  DONE// Steps:
// 1. If the length of the provided string is 0, an error should be returned
// 2. Split the given string on the commas present in it
// 3. Only 2 elements should be returned from the split, otherwise return an
//    error
// 4. Extract the first element from the split operation and use it as the name
// 5. Extract the other element from the split operation and parse it into a
//    `usize` as the age with something like `"4".parse::<usize>()`
// 6. If while extracting the name and the age something goes wrong, an error
//    should be returned
// If everything goes well, then return a Result of a Person object
//
// As an aside: `Box<dyn Error>` implements `From<&'_ str>`. This means that if
// you want to return a string error message, you can do so via just using
// return `Err("my error message".into())`.impl FromStr for Person {type Err = ParsePersonError;fn from_str(s: &str) -> Result<Person, Self::Err> {if s.len() ==0  {return Err(ParsePersonError::Empty)}let vecData: Vec<&str> = s.split(',').collect();if vecData.len() !=2 {return Err(ParsePersonError::BadLen)}let name=String::from(vecData[0]);if name.is_empty() {return Err(ParsePersonError::NoName)}// 如果姓名字符串能转成usize   就赋值给agelet age = match vecData[1].parse::<usize>() {Ok(age)=>age,Err(e) => return Err(ParsePersonError::ParseInt(e))};Ok(Person {name,age})}
}fn main() {let p = "Mark,20".parse::<Person>().unwrap();println!("{:?}", p);
}#[cfg(test)]
mod tests {use super::*;#[test]fn empty_input() {assert_eq!("".parse::<Person>(), Err(ParsePersonError::Empty));}#[test]fn good_input() {let p = "John,32".parse::<Person>();assert!(p.is_ok());let p = p.unwrap();assert_eq!(p.name, "John");assert_eq!(p.age, 32);}#[test]fn missing_age() {assert!(matches!("John,".parse::<Person>(),Err(ParsePersonError::ParseInt(_))));}#[test]fn invalid_age() {assert!(matches!("John,twenty".parse::<Person>(),Err(ParsePersonError::ParseInt(_))));}#[test]fn missing_comma_and_age() {assert_eq!("John".parse::<Person>(), Err(ParsePersonError::BadLen));}#[test]fn missing_name() {assert_eq!(",1".parse::<Person>(), Err(ParsePersonError::NoName));}#[test]fn missing_name_and_age() {assert!(matches!(",".parse::<Person>(),Err(ParsePersonError::NoName | ParsePersonError::ParseInt(_))));}#[test]fn missing_name_and_invalid_age() {assert!(matches!(",one".parse::<Person>(),Err(ParsePersonError::NoName | ParsePersonError::ParseInt(_))));}#[test]fn trailing_comma() {assert_eq!("John,32,".parse::<Person>(), Err(ParsePersonError::BadLen));}#[test]fn trailing_comma_and_some_string() {assert_eq!("John,32,man".parse::<Person>(),Err(ParsePersonError::BadLen));}
}

88.判断rgb的合法范围

话说没看出来try的用处在哪里

// try_from_into.rs
//
// TryFrom is a simple and safe type conversion that may fail in a controlled
// way under some circumstances. Basically, this is the same as From. The main
// difference is that this should return a Result type instead of the target
// type itself. You can read more about it at
// https://doc.rust-lang.org/std/convert/trait.TryFrom.html
//
// Execute `rustlings hint try_from_into` or use the `hint` watch subcommand for
// a hint.use std::convert::{TryFrom, TryInto};#[derive(Debug, PartialEq)]
struct Color {red: u8,green: u8,blue: u8,
}// We will use this error type for these `TryFrom` conversions.
#[derive(Debug, PartialEq)]
enum IntoColorError {// Incorrect length of sliceBadLen,// Integer conversion errorIntConversion,
}// I AM NOT DONE// Your task is to complete this implementation and return an Ok result of inner
// type Color. You need to create an implementation for a tuple of three
// integers, an array of three integers, and a slice of integers.
//
// Note that the implementation for tuple and array will be checked at compile
// time, but the slice implementation needs to check the slice length! Also note
// that correct RGB color values must be integers in the 0..=255 range.// Tuple implementation
impl TryFrom<(i16, i16, i16)> for Color {type Error = IntoColorError;fn try_from(tuple: (i16, i16, i16)) -> Result<Self, Self::Error> {if tuple.0>255 || tuple.0<0 ||tuple.1>255 || tuple.1<0 ||tuple.2>255 || tuple.2<0 {return Err(IntoColorError::IntConversion)}Ok(Color {red: tuple.0 as u8,green: tuple.1 as u8,blue: tuple.2 as u8,})}
}// Array implementation
impl TryFrom<[i16; 3]> for Color {type Error = IntoColorError;fn try_from(arr: [i16; 3]) -> Result<Self, Self::Error> {if arr[0]<0 || arr[0]>255 || arr[1]<0 ||arr[1]>255 || arr[2]<0 ||arr[2]>255  {return Err(IntoColorError::IntConversion)}Ok(Color {red: arr[0] as u8,green: arr[1] as u8,blue: arr[2] as u8,})}
}// Slice implementation
impl TryFrom<&[i16]> for Color {type Error = IntoColorError;fn try_from(slice: &[i16]) -> Result<Self, Self::Error> {if slice.len()!=3 {return Err(IntoColorError::BadLen)}if slice[0]<0 || slice[0]>255 ||slice[1]<0 || slice[1]>255 ||slice[2]<0 || slice[2]>255 {return Err(IntoColorError::IntConversion)}Ok(Color {red: slice[0] as u8,green: slice[1] as u8,blue: slice[2] as u8,})}
}fn main() {// Use the `try_from` functionlet c1 = Color::try_from((183, 65, 14));println!("{:?}", c1);// Since TryFrom is implemented for Color, we should be able to use TryIntolet c2: Result<Color, _> = [183, 65, 14].try_into();println!("{:?}", c2);let v = vec![183, 65, 14];// With slice we should use `try_from` functionlet c3 = Color::try_from(&v[..]);println!("{:?}", c3);// or take slice within round brackets and use TryIntolet c4: Result<Color, _> = (&v[..]).try_into();println!("{:?}", c4);
}#[cfg(test)]
mod tests {use super::*;#[test]fn test_tuple_out_of_range_positive() {assert_eq!(Color::try_from((256, 1000, 10000)),Err(IntoColorError::IntConversion));}#[test]fn test_tuple_out_of_range_negative() {assert_eq!(Color::try_from((-1, -10, -256)),Err(IntoColorError::IntConversion));}#[test]fn test_tuple_sum() {assert_eq!(Color::try_from((-1, 255, 255)),Err(IntoColorError::IntConversion));}#[test]fn test_tuple_correct() {let c: Result<Color, _> = (183, 65, 14).try_into();assert!(c.is_ok());assert_eq!(c.unwrap(),Color {red: 183,green: 65,blue: 14});}#[test]fn test_array_out_of_range_positive() {let c: Result<Color, _> = [1000, 10000, 256].try_into();assert_eq!(c, Err(IntoColorError::IntConversion));}#[test]fn test_array_out_of_range_negative() {let c: Result<Color, _> = [-10, -256, -1].try_into();assert_eq!(c, Err(IntoColorError::IntConversion));}#[test]fn test_array_sum() {let c: Result<Color, _> = [-1, 255, 255].try_into();assert_eq!(c, Err(IntoColorError::IntConversion));}#[test]fn test_array_correct() {let c: Result<Color, _> = [183, 65, 14].try_into();assert!(c.is_ok());assert_eq!(c.unwrap(),Color {red: 183,green: 65,blue: 14});}#[test]fn test_slice_out_of_range_positive() {let arr = [10000, 256, 1000];assert_eq!(Color::try_from(&arr[..]),Err(IntoColorError::IntConversion));}#[test]fn test_slice_out_of_range_negative() {let arr = [-256, -1, -10];assert_eq!(Color::try_from(&arr[..]),Err(IntoColorError::IntConversion));}#[test]fn test_slice_sum() {let arr = [-1, 255, 255];assert_eq!(Color::try_from(&arr[..]),Err(IntoColorError::IntConversion));}#[test]fn test_slice_correct() {let v = vec![183, 65, 14];let c: Result<Color, _> = Color::try_from(&v[..]);assert!(c.is_ok());assert_eq!(c.unwrap(),Color {red: 183,green: 65,blue: 14});}#[test]fn test_slice_excess_length() {let v = vec![0, 0, 0, 0];assert_eq!(Color::try_from(&v[..]), Err(IntoColorError::BadLen));}#[test]fn test_slice_insufficient_length() {let v = vec![0, 0];assert_eq!(Color::try_from(&v[..]), Err(IntoColorError::BadLen));}
}

89.as_ref与as_mut

as_ref用于将值转为引用

as_mut用于将值转为可变引用

在pow操作的时候需要一个拥有所有权的对象,所以需要调用as_mut方法

差不多是这个意思

// as_ref_mut.rs
//
// AsRef and AsMut allow for cheap reference-to-reference conversions. Read more
// about them at https://doc.rust-lang.org/std/convert/trait.AsRef.html and
// https://doc.rust-lang.org/std/convert/trait.AsMut.html, respectively.
//
// Execute `rustlings hint as_ref_mut` or use the `hint` watch subcommand for a
// hint.// I AM NOT DONE// Obtain the number of bytes (not characters) in the given argument.
// TODO: Add the AsRef trait appropriately as a trait bound.
fn byte_counter<T:AsRef<str>>(arg: T) -> usize {arg.as_ref().as_bytes().len()
}// Obtain the number of characters (not bytes) in the given argument.
// TODO: Add the AsRef trait appropriately as a trait bound.
fn char_counter<T:AsRef<str>>(arg: T) -> usize {arg.as_ref().chars().count()
}// Squares a number using as_mut().
// TODO: Add the appropriate trait bound.
fn num_sq<T:AsMut<u32>>(arg: &mut T) {// TODO: Implement the function body.let availableValue =arg.as_mut();(*availableValue)=(*availableValue).pow(2)
}#[cfg(test)]
mod tests {use super::*;#[test]fn different_counts() {let s = "Café au lait";assert_ne!(char_counter(s), byte_counter(s));}#[test]fn same_counts() {let s = "Cafe au lait";assert_eq!(char_counter(s), byte_counter(s));}#[test]fn different_counts_using_string() {let s = String::from("Café au lait");assert_ne!(char_counter(s.clone()), byte_counter(s));}#[test]fn same_counts_using_string() {let s = String::from("Cafe au lait");assert_eq!(char_counter(s.clone()), byte_counter(s));}#[test]fn mult_box() {let mut num: Box<u32> = Box::new(3);num_sq(&mut num);assert_eq!(*num, 9);}
}

90.一个完全蒙蔽的题目

GPT给我的答案

unsafe 关键字告诉编译器，这段代码可能包含不安全的操作，需要开发人员自己来确保其正确性和安全性。

• let mut t：这是一个变量声明，声明了一个名为 t 的可变变量。t 的类型是 &mut u32，即一个可变的对 u32 类型的引用。

• &mut *(address as *mut u32)：这部分是一个复杂的表达式，用于将 address 强制类型转换为 *mut u32，然后进行解引用。具体来说：

  • address as *mut u32 将 address 转换为一个 *mut u32 类型的指针。这个指针表示一个指向 u32 类型的可变内存地址。
  • &mut * 是解引用操作符，它将指针解引用，以获取指针指向的值。

• *t = 0xAABBCCDD：这是将 t 所引用的内存位置设置为 0xAABBCCDD 的值。由于 t 是可变引用，因此可以通过 *t 来修改内存中的值

// tests5.rs
//
// An `unsafe` in Rust serves as a contract.
//
// When `unsafe` is marked on an item declaration, such as a function,
// a trait or so on, it declares a contract alongside it. However,
// the content of the contract cannot be expressed only by a single keyword.
// Hence, its your responsibility to manually state it in the `# Safety`
// section of your documentation comment on the item.
//
// When `unsafe` is marked on a code block enclosed by curly braces,
// it declares an observance of some contract, such as the validity of some
// pointer parameter, the ownership of some memory address. However, like
// the text above, you still need to state how the contract is observed in
// the comment on the code block.
//
// NOTE: All the comments are for the readability and the maintainability of
// your code, while the Rust compiler hands its trust of soundness of your
// code to yourself! If you cannot prove the memory safety and soundness of
// your own code, take a step back and use safe code instead!
//
// Execute `rustlings hint tests5` or use the `hint` watch subcommand for a
// hint.// I AM NOT DONE/// # Safety
///
/// The `address` must contain a mutable reference to a valid `u32` value.
unsafe fn modify_by_address(address: usize) {// TODO: Fill your safety notice of the code block below to match your// code's behavior and the contract of this function. You may use the// comment of the test below as your format reference.unsafe {// todo!("Your code goes here")let mut t = &mut *(&mut *(address as *mut u32) as *mut u32); *t=0xAABBCCDD}
}#[cfg(test)]
mod tests {use super::*;#[test]fn test_success() {let mut t: u32 = 0x12345678;// SAFETY: The address is guaranteed to be valid and contains// a unique reference to a `u32` local variable.unsafe { modify_by_address(&mut t as *mut u32 as usize) };assert!(t == 0xAABBCCDD);}
}