add solutions for string.md
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sunface
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@ -0,0 +1,174 @@
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1.
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```rust
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fn main() {
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let s: &str = "hello, world";
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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: Box<str> = "hello, world".into();
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greetings(&s)
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}
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fn greetings(s: &str) {
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println!("{}",s)
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}
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```
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3.
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```rust
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fn main() {
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let mut s = String::new();
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s.push_str("hello, world");
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s.push('!');
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assert_eq!(s, "hello, world!");
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}
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```
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4.
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```rust
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fn main() {
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let mut s = String::from("hello");
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s.push(',');
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s.push_str(" world");
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s += "!";
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println!("{}", s)
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}
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```
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5.
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```rust
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fn main() {
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let s = String::from("I like dogs");
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// Allocate new memory and store the modified string there
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let s1 = s.replace("dogs", "cats");
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assert_eq!(s1, "I like cats")
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}
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```
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6.
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```rust
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fn main() {
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let s1 = String::from("hello,");
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let s2 = String::from("world!");
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let s3 = s1.clone() + &s2;
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assert_eq!(s3,"hello,world!");
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println!("{}",s1);
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}
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```
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7.
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```rust
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fn main() {
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let s = "hello, world".to_string();
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greetings(s)
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}
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fn greetings(s: String) {
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println!("{}",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 s = String::from("hello, world");
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greetings(s)
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}
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fn greetings(s: String) {
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println!("{}",s)
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}
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```
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8.
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```rust
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fn main() {
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let s = "hello, world".to_string();
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let s1: &str = &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 s = "hello, world";
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let s1: &str = 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 s = "hello, world".to_string();
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let s1: String = s;
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}
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```
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9.
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```rust
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fn main() {
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// You can use escapes to write bytes by their hexadecimal values
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// fill the blank below to show "I'm writing Rust"
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let byte_escape = "I'm writing Ru\x73\x74!";
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println!("What are you doing\x3F (\\x3F means ?) {}", byte_escape);
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// ...or Unicode code points.
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let unicode_codepoint = "\u{211D}";
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let character_name = "\"DOUBLE-STRUCK CAPITAL R\"";
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println!("Unicode character {} (U+211D) is called {}",
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unicode_codepoint, character_name );
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let long_string = "String literals
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can span multiple lines.
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The linebreak and indentation here \
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can be escaped too!";
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println!("{}", long_string);
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}
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```
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10.
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```rust
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fn main() {
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let raw_str = "Escapes don't work here: \x3F \u{211D}";
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// modify below line to make it work
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assert_eq!(raw_str, "Escapes don't work here: ? ℝ");
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// If you need quotes in a raw string, add a pair of #s
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let quotes = r#"And then I said: "There is no escape!""#;
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println!("{}", quotes);
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// If you need "# in your string, just use more #s in the delimiter.
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// You can use up to 65535 #s.
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let delimiter = r###"A string with "# in it. And even "##!"###;
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println!("{}", delimiter);
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// fill the blank
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let long_delimiter = r###"Hello, "##""###;
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assert_eq!(long_delimiter, "Hello, \"##\"")
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}
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```
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11.
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```rust
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fn main() {
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let s1 = String::from("hi,中国");
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let h = &s1[0..1];
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assert_eq!(h, "h");
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let h1 = &s1[3..6];
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assert_eq!(h1, "中");
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}
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```
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12.
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```rust
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fn main() {
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for c in "你好，世界".chars() {
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println!("{}", c)
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}
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}
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```
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1.
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```rust
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fn main() {
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let x = 5;
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// fill the blank
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let p = &x;
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println!("the memory address of x is {:p}", p); // one possible output: 0x16fa3ac84
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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 x = 5;
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let y = &x;
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// modify this line only
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assert_eq!(5, *y);
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}
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```
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3.
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```rust
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fn main() {
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let mut s = String::from("hello, ");
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borrow_object(&s)
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}
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fn borrow_object(s: &String) {}
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```
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4.
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```rust
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fn main() {
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let mut s = String::from("hello, ");
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push_str(&mut s)
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}
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fn push_str(s: &mut String) {
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s.push_str("world")
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}
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```
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5.
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```rust
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fn main() {
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let mut s = String::from("hello, ");
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// fill the blank to make it work
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let p = &mut s;
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p.push_str("world");
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}
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```
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6.
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```rust
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fn main() {
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let c = '中';
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let r1 = &c;
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// fill the blank，dont change other code
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let ref r2 = c;
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assert_eq!(*r1, *r2);
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// check the equality of the two address strings
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assert_eq!(get_addr(r1),get_addr(r2));
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}
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// get memory address string
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fn get_addr(r: &char) -> String {
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format!("{:p}", r)
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}
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```
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7.
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```rust
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fn main() {
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let s = String::from("hello");
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let r1 = &s;
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let r2 = &s;
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println!("{}, {}", r1, r2);
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}
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```
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8.
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```rust
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fn main() {
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//fix error by modifying this line
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let mut s = String::from("hello, ");
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borrow_object(&mut s)
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}
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fn borrow_object(s: &mut String) {}
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```
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9.
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```rust
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fn main() {
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let mut s = String::from("hello, ");
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borrow_object(&s);
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s.push_str("world");
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}
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fn borrow_object(s: &String) {}
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```
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10.
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```rust
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fn main() {
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let mut s = String::from("hello, ");
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let r1 = &mut s;
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r1.push_str("world");
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let r2 = &mut s;
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r2.push_str("!");
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// println!("{}",r1);
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}
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```
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11.
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```rust
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fn main() {
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let mut s = String::from("hello, ");
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let r1 = &mut s;
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let r2 = &mut s;
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// add one line below to make a compiler error: cannot borrow `s` as mutable more than once at a time
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// you can't use r1 and r2 at the same time
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r1.push_str("world");
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}
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```
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@ -3,7 +3,7 @@ The type of string literal `"hello, world"` is `&str`, e.g `let s: &str = "hello
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### str and &str
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🌟 We can't use `str` type in normal ways, but we can use `&str`
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1. 🌟 We can't use `str` type in normal ways, but we can use `&str`
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```rust,editable
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@ -14,7 +14,7 @@ fn main() {
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```
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🌟🌟🌟 We can only use `str` by boxed it, `&` can be used to convert `Box<str>` to `&str`
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2. 🌟🌟 We can only use `str` by boxed it, `&` can be used to convert `Box<str>` to `&str`
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```rust,editable
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### String
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`String` type is defined in std and 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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🌟
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3. 🌟
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```rust,editable
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// fill the blank
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}
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```
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🌟🌟🌟
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4. 🌟🌟🌟
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```rust,editable
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// fix all errors without adding newline
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fn main() {
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let s = String::from("hello");
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s.push(',');`
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s.push(',');
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s.push(" world");
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s += "!".to_string();
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@ -59,7 +59,7 @@ fn main() {
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}
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```
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🌟🌟 `replace` can be used to replace substring
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5. 🌟🌟 `replace` can be used to replace substring
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```rust,editable
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// fill the blank
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@ -74,11 +74,11 @@ fn main() {
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More `String` methods can be found under [String](https://doc.rust-lang.org/std/string/struct.String.html) module.
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🌟🌟 You can only concat a `String` with `&str`, and `String`'s ownership can be moved to another variable
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6. 🌟🌟 You can only concat a `String` with `&str`, and `String`'s ownership can be moved to another variable
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```rust,editable
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// fix errors
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// fix errors without removing any line
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fn main() {
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let s1 = String::from("hello,");
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let s2 = String::from("world!");
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@ -91,7 +91,7 @@ fn main() {
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### &str and String
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Opsite to the seldom using of `str`, `&str` and `String` are used everywhere!
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🌟🌟 `&str` can be converted to `String` in two ways
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7. 🌟🌟 `&str` can be converted to `String` in two ways
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```rust,editable
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// fix error with at lest two solutions
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@ -105,7 +105,7 @@ fn greetings(s: String) {
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}
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```
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🌟🌟 We can use `String::from` or `to_string` to convert a `&str` to `String`
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8. 🌟🌟 We can use `String::from` or `to_string` to convert a `&str` to `String`
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```rust,editable
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@ -117,7 +117,7 @@ fn main() {
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```
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### string escapes
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🌟
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9. 🌟
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```rust,editable
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fn main() {
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// You can use escapes to write bytes by their hexadecimal values
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@ -140,7 +140,7 @@ fn main() {
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}
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```
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🌟🌟🌟 Sometimes there are just too many characters that need to be escaped or it's just much more convenient to write a string out as-is. This is where raw string literals come into play.
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10. 🌟🌟🌟 Sometimes there are just too many characters that need to be escaped or it's just much more convenient to write a string out as-is. This is where raw string literals come into play.
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```rust,editable
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@ -211,7 +211,7 @@ fn main() {
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A more detailed listing of the ways to write string literals and escape characters is given in the ['Tokens' chapter](https://doc.rust-lang.org/reference/tokens.html) of the Rust Reference.
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### string index
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🌟🌟 You can't use index to access a char in a string, but you can use slice `&s1[start..end]`.
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11. 🌟🌟🌟 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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@ -226,7 +226,7 @@ fn main() {
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```
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### operate on UTF8 string
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🌟
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12. 🌟
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```rust,editable
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fn main() {
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@ -1,7 +1,7 @@
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# Reference and Borrowing
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### Reference
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🌟
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1. 🌟
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```rust,editable
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fn main() {
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@ -9,11 +9,11 @@ fn main() {
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// fill the blank
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let p = __;
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println!("the memory address of x is {:p}", p); // output: 0x16fa3ac84
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println!("the memory address of x is {:p}", p); // one possible output: 0x16fa3ac84
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}
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```
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🌟
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2. 🌟
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```rust,editable
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fn main() {
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@ -25,7 +25,7 @@ fn main() {
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}
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```
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🌟
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3. 🌟
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```rust,editable
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// fix error
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@ -38,20 +38,22 @@ fn main() {
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fn borrow_object(s: &String) {}
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```
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🌟
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4. 🌟
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```rust,editable
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// fix error
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fn main() {
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let mut s = String::from("hello, ");
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borrow_object(&s)
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push_str(s)
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}
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fn borrow_object(s: &mut String) {}
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fn push_str(s: &mut String) {
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s.push_str("world")
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}
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```
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🌟🌟
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5. 🌟🌟
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```rust,editable
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fn main() {
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@ -67,7 +69,7 @@ fn main() {
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#### ref
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`ref` can be used to take references to a value, similar to `&`.
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🌟🌟🌟
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6. 🌟🌟🌟
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```rust,editable
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fn main() {
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@ -90,7 +92,7 @@ fn get_addr(r: &char) -> String {
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```
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### Borrowing rules
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🌟
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7. 🌟
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```rust,editable
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// remove something to make it work
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@ -106,7 +108,7 @@ fn main() {
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```
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#### Mutablity
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🌟 Error: Borrow a immutable object as mutable
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8. 🌟 Error: Borrow a immutable object as mutable
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```rust,editable
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fn main() {
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@ -119,7 +121,7 @@ fn main() {
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fn borrow_object(s: &mut String) {}
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```
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🌟🌟 Ok: Borrow a mutable object as immutable
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9. 🌟🌟 Ok: Borrow a mutable object as immutable
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```rust,editable
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// this code has no errors!
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@ -135,7 +137,7 @@ fn borrow_object(s: &String) {}
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```
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### NLL
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🌟🌟
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10. 🌟🌟
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```rust,editable
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// comment one line to make it work
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|
|
@ -151,7 +153,7 @@ fn main() {
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}
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```
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🌟🌟🌟
|
||||
11. 🌟🌟
|
||||
```rust,editable
|
||||
|
||||
fn main() {
|
||||
|
|
|
|||
|
|
@ -14,7 +14,7 @@ fn main() {
|
|||
```
|
||||
|
||||
|
||||
🌟🌟🌟 如果要使用 `str` 类型，只能配合 `Box`。 `&` 可以用来将 `Box<str>` 转换为 `&str` 类型
|
||||
🌟🌟 如果要使用 `str` 类型，只能配合 `Box`。 `&` 可以用来将 `Box<str>` 转换为 `&str` 类型
|
||||
|
||||
```rust,editable
|
||||
|
||||
|
|
@ -51,7 +51,7 @@ fn main() {
|
|||
// 修复所有错误，并且不要新增代码行
|
||||
fn main() {
|
||||
let s = String::from("hello");
|
||||
s.push(',');`
|
||||
s.push(',');
|
||||
s.push(" world");
|
||||
s += "!".to_string();
|
||||
|
||||
|
|
@ -79,7 +79,7 @@ fn main() {
|
|||
|
||||
```rust,editable
|
||||
|
||||
// 修复所有错误
|
||||
// 修复所有错误，不要删除任何一行代码
|
||||
fn main() {
|
||||
let s1 = String::from("hello,");
|
||||
let s2 = String::from("world!");
|
||||
|
|
|
|||
|
|
@ -45,10 +45,12 @@ fn borrow_object(s: &String) {}
|
|||
fn main() {
|
||||
let mut s = String::from("hello, ");
|
||||
|
||||
borrow_object(&s)
|
||||
push_str(s)
|
||||
}
|
||||
|
||||
fn borrow_object(s: &mut String) {}
|
||||
fn push_str(s: &mut String) {
|
||||
s.push_str("world")
|
||||
}
|
||||
```
|
||||
|
||||
🌟🌟
|
||||
|
|
@ -151,7 +153,7 @@ fn main() {
|
|||
}
|
||||
```
|
||||
|
||||
🌟🌟🌟
|
||||
🌟🌟
|
||||
```rust,editable
|
||||
|
||||
fn main() {
|
||||
|
|
|
|||
Loading…
Reference in New Issue