add string.md
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1.
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```rust
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fn main() {
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let mut s: String = String::from("hello, ");
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s.push_str("world");
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s.push('!');
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move_ownership(s.clone());
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assert_eq!(s, "hello, world!");
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println!("Success!")
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}
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fn move_ownership(s: String) {
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println!("ownership of \"{}\" is moved here!", s)
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}
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```
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```rust
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fn main() {
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let mut s: String = String::from("hello, ");
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s.push_str("world");
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s.push('!');
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borrow_string(&s);
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assert_eq!(s, "hello, world!");
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println!("Success!")
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}
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fn borrow_string(s: &str) {
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println!("ownership of \"{}\" is moved here!", s)
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}
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```
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2.
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```rust
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// FILL in the blanks
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fn main() {
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// get a slice of String with reference: String -> &str
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let mut s = String::from("hello, world");
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let slice1: &str = &s; // in two ways
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assert_eq!(slice1, "hello, world");
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let slice2 = &s[0..5];
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assert_eq!(slice2, "hello");
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//Note! The type here cant be `&mut str` due to `push` is ONLY defined on String type and its mut reference: `&mut String` !
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// So you can't use `s.as_mut_str()`
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let slice3: &mut String = &mut s;
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slice3.push('!');
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assert_eq!(slice3, "hello, world!");
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println!("Success!")
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}
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```
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```rust
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fn main() {
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let mut s = String::from("hello, world");
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let slice1: &str = s.as_str();
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assert_eq!(slice1, "hello, world");
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let slice2 = &s[0..5];
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assert_eq!(slice2, "hello");
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//Note! The type here cant be `&mut str` due to `push` is ONLY defined on String type and its mut reference: `&mut String` !
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// So you can't use `s.as_mut_str()`
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let slice3: &mut String = &mut s;
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slice3.push('!');
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assert_eq!(slice3, "hello, world!");
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println!("Success!")
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}
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```
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2.
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```rust
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fn main() {
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let s = String::from("hello, ไธ็");
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let slice1 = &s[0..1]; //modify this line to fix the error, tips: `h` only takes 1 byte in UTF8 format
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assert_eq!(slice1, "h");
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let slice2 = &s[7..10];//modify this line to fix the error, tips: `ไธญ` takes 3 bytes in UTF8 format
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assert_eq!(slice2, "ไธ");
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println!("Success!")
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}
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```
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3.
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```rust
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// FILL in the blanks
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fn main() {
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let mut s = String::new();
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s.push_str("hello");
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// some bytes, in a vector
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let v = vec![104, 101, 108, 108, 111];
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// Turn a bytes vector into a String
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// We know these bytes are valid, so we'll use `unwrap()`.
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let s1 = String::from_utf8(v).unwrap();
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assert_eq!(s, s1);
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println!("Success!")
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}
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```
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@ -28,10 +28,10 @@
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- [Traits](generics-traits/traits.md)
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- [Trait Object](generics-traits/trait-object.md)
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- [Advanced Traits](generics-traits/advanced-traits.md)
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- [Collection Types todo](collections/intro.md)
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- [Collection Types](collections/intro.md)
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- [String](collections/string.md)
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- [Vector](collections/vector.md)
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- [HashMap](collections/hashmap.md)
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- [Vector todo](collections/vector.md)
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- [HashMap todo](collections/hashmap.md)
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- [Type Conversion todo](type-conversion.md)
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- [Result and panic todo](result-panic/intro.md)
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- [panic!](result-panic/panic.md)
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@ -1 +1,6 @@
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# Collection Types
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Learning resources:
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- English: [Rust Book Chapter 8](https://doc.rust-lang.org/book/ch08-00-common-collections.html)
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- ็ฎไฝไธญๆ: [Rust่ฏญ่จๅฃ็ป - ้ๅ็ฑปๅ](https://course.rs/basic/collections/intro.html)
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@ -1 +1,111 @@
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# String
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`std::string::String` is a UTF-8 encoded, growable string. It is the most common string type we used in daily dev, it also has ownership over the string contents.
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### Basic operations
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1. ๐๐
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```rust,editable
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// FILL in the blanks and FIX errors
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// 1. Don't use `to_string()`
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// 2. Dont't add/remove any code line
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fn main() {
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let mut s: String = "hello, ";
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s.push_str("world".to_string());
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s.push(__);
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move_ownership(s);
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assert_eq!(s, "hello, world!");
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println!("Success!")
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}
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fn move_ownership(s: String) {
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println!("ownership of \"{}\" is moved here!", s)
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}
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```
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### String and &str
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A `String` is stored as a vector of bytes (`Vec<u8>`), but guaranteed to always be a valid UTF-8 sequence. `String` is heap allocated, growable and not null terminated.
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`&str` is a slice (`&[u8]`) that always points to a valid UTF-8 sequence, and can be used to view into a String, just like `&[T]` is a view into `Vec<T>`.
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2. ๐๐
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```rust,editable
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// FILL in the blanks
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fn main() {
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// get a slice of String with reference: String -> &str
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let mut s = String::from("hello, world");
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let slice1: &str = __; // in two ways
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assert_eq!(slice1, "hello, world");
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let slice2 = __;
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assert_eq!(slice2, "hello");
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let slice3: __ = __;
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slice3.push('!');
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assert_eq!(slice3, "hello, world!");
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println!("Success!")
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}
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```
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### UTF-8 & Indexing
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Strings are always valid UTF-8. This has a few implications:
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- the first of which is that if you need a non-UTF-8 string, consider [OsString](https://doc.rust-lang.org/stable/std/ffi/struct.OsString.html). It is similar, but without the UTF-8 constraint.
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- The second implication is that you cannot index into a String
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Indexing is intended to be a constant-time operation, but UTF-8 encoding does not allow us to do this. Furthermore, itโs not clear what sort of thing the index should return: a byte, a codepoint, or a grapheme cluster. The bytes and chars methods return iterators over the first two, respectively.
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2. ๐๐๐ You can't use index to access a char in a string, but you can use slice `&s1[start..end]`.
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```rust,editable
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// FIX errors
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fn main() {
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let s = String::from("hello, ไธ็");
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let slice1 = s[0]; //tips: `h` only takes 1 byte in UTF8 format
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assert_eq!(slice1, "h");
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let slice2 = &s[3..5];// tips: `ไธญ` takes 3 bytes in UTF8 format
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assert_eq!(slice2, "ไธ");
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println!("Success!")
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}
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```
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3. ๐๐๐
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> Tips: maybe you need `from_utf8` method
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```rust,editable
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// FILL in the blanks
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fn main() {
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let mut s = String::new();
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__;
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// some bytes, in a vector
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let v = vec![104, 101, 108, 108, 111];
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// Turn a bytes vector into a String
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// We know these bytes are valid, so we'll use `unwrap()`.
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let s1 = __;
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assert_eq!(s, s1);
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println!("Success!")
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}
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```
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### Representation
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### Common methods
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