154 lines
2.0 KiB
Markdown
154 lines
2.0 KiB
Markdown
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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``` |