Merge pull request #287 from Tanish-Eagle/edit
Edited type-conversionEdit
This commit is contained in:
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bce4f2116f
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@ -15,7 +15,7 @@ fn main() {
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assert_eq!(integer, 'b' as u8);
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println!("Success!")
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println!("Success!");
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}
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```
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@ -23,17 +23,17 @@ fn main() {
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```rust,editable
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fn main() {
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assert_eq!(u8::MAX, 255);
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// the max of `u8` is 255 as shown above.
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// The max of `u8` is 255 as shown above.
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// so the below code will cause an overflow error: literal out of range for `u8`.
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// PLEASE looking for clues within compile errors to FIX it.
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// DON'T modify any code in main.
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let v = 1000 as u8;
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println!("Success!")
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println!("Success!");
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}
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```
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3. ππ when casting any value to an unsigned type `T`, `T::MAX + 1` is added or subtracted until the value fits into the new type.
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3. ππ When casting any value to an unsigned type `T`, `T::MAX + 1` is added or subtracted until the value fits into the new type.
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```rust,editable
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fn main() {
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assert_eq!(1000 as u16, __);
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@ -67,7 +67,7 @@ fn main() {
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}
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```
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4. πππ Raw pointer can be converted to memory address (integer) and vice versa
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4. πππ Raw pointers can be converted to memory address (integer) and vice versa.
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```rust,editable
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// FILL in the blanks
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@ -78,13 +78,13 @@ fn main() {
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let second_address = first_address + 4; // 4 == std::mem::size_of::<i32>()
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let p2: *mut i32 = second_address __; // p2 points to the 2nd element in values
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unsafe {
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// add one to the second element
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// Add one to the second element
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__
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}
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assert_eq!(values[1], 3);
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println!("Success!")
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println!("Success!");
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}
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```
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@ -100,6 +100,6 @@ fn main() {
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assert_eq!(std::mem::size_of_val(&*b), __)
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}
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println!("Success!")
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println!("Success!");
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}
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```
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@ -8,7 +8,7 @@ The `Into` trait is simply the reciprocal of the `From` trait. That is, if you h
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Using the `Into` trait will typically require the type annotations as the compiler is unable to determine this most of the time.
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For example we can easily convert `&str` into `String` :
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For example, we can easily convert `&str` into `String` :
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```rust
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fn main() {
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let my_str = "hello";
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@ -16,12 +16,12 @@ fn main() {
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// three conversions below all depends on the fact: String implements From<&str>:
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let string1 = String::from(my_str);
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let string2 = my_str.to_string();
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// explict type annotation is required here
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// Explicit type annotation is required here
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let string3: String = my_str.into();
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}
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```
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because the standard library has already implemented this for us : `impl From<&'_ str> for String` .
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Because the standard library has already implemented this for us : `impl From<&'_ str> for String` .
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Some implementations of `From` trait can be found [here](https://doc.rust-lang.org/stable/std/convert/trait.From.html#implementors).
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@ -43,7 +43,7 @@ fn main() {
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// FIX the error in two ways
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let s: String = 'a' as String;
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println!("Success!")
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println!("Success!");
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}
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```
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@ -71,7 +71,7 @@ fn main() {
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let num: Number = __;
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assert_eq!(num.value, 30);
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println!("Success!")
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println!("Success!");
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}
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```
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@ -104,7 +104,7 @@ fn open_and_parse_file(file_name: &str) -> Result<i32, CliError> {
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}
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fn main() {
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println!("Success!")
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println!("Success!");
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}
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```
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@ -134,7 +134,7 @@ fn main() {
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assert_eq!(n, __);
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println!("Success!")
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println!("Success!");
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}
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```
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@ -166,6 +166,6 @@ fn main() {
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let result: Result<EvenNum, ()> = 5i32.try_into();
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assert_eq!(result, __);
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println!("Success!")
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println!("Success!");
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}
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```
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@ -1,7 +1,7 @@
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# Others
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### Convert any type to String
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To convert any type to `String`, you can simply the `ToString` trait for that type. Rather than doing that directly, you should implement the `fmt::Display` trait which will automatically provides `ToString` and also allows you to print the type with `println!`.
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To convert any type to `String`, you can simply use the `ToString` trait for that type. Rather than doing that directly, you should implement the `fmt::Display` trait which will automatically provides `ToString` and also allows you to print the type with `println!`.
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1. ππ
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```rust,editable
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@ -22,14 +22,14 @@ fn main() {
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assert_eq!(origin.__, "The point is (0, 0)");
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assert_eq!(format!(__), "The point is (0, 0)");
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println!("Success!")
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println!("Success!");
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}
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```
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### Parse a String
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2. πππ We can use `parse` method to convert a `String` into a `i32` number, this is becuase `FromStr` is implemented for `i32` type in standard library: `impl FromStr for i32`
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2. πππ We can use `parse` method to convert a `String` into a `i32` number, this is because `FromStr` is implemented for `i32` type in standard library: `impl FromStr for i32`
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```rust,editable
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// To use `from_str` method, you needs to introduce this trait into the current scope.
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// To use `from_str` method, you need to introduce this trait into the current scope.
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use std::str::FromStr;
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fn main() {
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let parsed: i32 = "5".__.unwrap();
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@ -38,7 +38,7 @@ fn main() {
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let sum = parsed + turbo_parsed + from_str;
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assert_eq!(sum, 35);
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println!("Success!")
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println!("Success!");
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}
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```
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@ -74,14 +74,14 @@ fn main() {
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let p = __;
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assert_eq!(p.unwrap(), Point{ x: 3, y: 4} );
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println!("Success!")
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println!("Success!");
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}
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```
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### Deref
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You can find all the examples and exercises of the `Deref` trait [here](https://practice.rs/smart-pointers/deref.html).
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### transmute
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### Transmute
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`std::mem::transmute` is a **unsafe function** can be used to reinterprets the bits of a value of one type as another type. Both of the original and the result types must have the same size and neither of them can be invalid.
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`transmute` is semantically equivalent to a bitwise move of one type into another. It copies the bits from the source value into the destination value, then forgets the original, seems equivalent to C's `memcpy` under the hood.
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@ -126,9 +126,9 @@ fn main() {
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let num = unsafe { std::mem::transmute::<[u8; 4], u32>(raw_bytes) };
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// use `u32::from_ne_bytes` instead
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// Use `u32::from_ne_bytes` instead
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let num = u32::from_ne_bytes(raw_bytes);
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// or use `u32::from_le_bytes` or `u32::from_be_bytes` to specify the endianness
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// Or use `u32::from_le_bytes` or `u32::from_be_bytes` to specify the endianness
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let num = u32::from_le_bytes(raw_bytes);
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assert_eq!(num, 0x12345678);
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let num = u32::from_be_bytes(raw_bytes);
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@ -150,7 +150,7 @@ fn main() {
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let val_casts = unsafe { &mut *(ptr as *mut i32 as *mut u32) };
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/*Turning an &str into a &[u8]: */
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// this is not a good way to do this.
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// This is not a good way to do this.
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let slice = unsafe { std::mem::transmute::<&str, &[u8]>("Rust") };
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assert_eq!(slice, &[82, 117, 115, 116]);
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