add solutions for patterns.md

This commit is contained in:
sunface 2022-03-02 22:04:00 +08:00
parent 5807a3147d
commit 4ba73b3969
2 changed files with 93 additions and 5 deletions

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@ -0,0 +1,88 @@
1.
```rust
fn main() {}
fn match_number(n: i32) {
match n {
// match a single value
1 => println!("One!"),
// fill in the blank with `|`, DON'T use `..` ofr `..=`
2 | 3 | 4 | 5 => println!("match 2 -> 5"),
// match an inclusive range
6..=10 => {
println!("match 6 -> 10")
},
_ => {
println!("match 11 -> +infinite")
}
}
}
```
2.
```rust
struct Point {
x: i32,
y: i32,
}
fn main() {
// fill in the blank to let p match the second arm
let p = Point { x: 2, y: 20 }; // x can be [0, 5], y can be 10 20 or 30
match p {
Point { x, y: 0 } => println!("On the x axis at {}", x),
// second arm
Point { x: 0..=5, y: y@ (10 | 20 | 30) } => println!("On the y axis at {}", y),
Point { x, y } => println!("On neither axis: ({}, {})", x, y),
}
}
```
3.
```rust
enum Message {
Hello { id: i32 },
}
fn main() {
let msg = Message::Hello { id: 5 };
match msg {
Message::Hello {
id: id@3..=7,
} => println!("Found an id in range [3, 7]: {}", id),
Message::Hello { id: newid@(10 | 11 | 12) } => {
println!("Found an id in another range [10, 12]: {}", newid)
}
Message::Hello { id } => println!("Found some other id: {}", id),
}
}
```
4.
```rust
fn main() {
let num = Some(4);
let split = 5;
match num {
Some(x) if x < split => assert!(x < split),
Some(x) => assert!(x >= split),
None => (),
}
}
```
5.
```rust
fn main() {
let numbers = (2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048);
match numbers {
(first,..,last) => {
assert_eq!(first, 2);
assert_eq!(last, 2048);
}
}
}
```

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@ -1,6 +1,6 @@
# Patterns
🌟🌟 use `|` to match several values, use `..=` to match a inclusive range
1. 🌟🌟 use `|` to match several values, use `..=` to match a inclusive range
```rust,editable
fn main() {}
@ -21,7 +21,7 @@ fn match_number(n: i32) {
}
```
🌟🌟🌟 The `@` operator lets us create a variable that holds a value at the same time we are testing that value to see whether it matches a pattern.
2. 🌟🌟🌟 The `@` operator lets us create a variable that holds a value at the same time we are testing that value to see whether it matches a pattern.
```rust,editable
struct Point {
@ -42,7 +42,7 @@ fn main() {
}
```
🌟🌟🌟
3. 🌟🌟🌟
```rust,editable
@ -66,7 +66,7 @@ fn main() {
}
```
🌟🌟 A match guard is an additional if condition specified after the pattern in a match arm that must also match, along with the pattern matching, for that arm to be chosen.
4. 🌟🌟 A match guard is an additional if condition specified after the pattern in a match arm that must also match, along with the pattern matching, for that arm to be chosen.
```rust,editable
// fill in the blank to make the code work, `split` MUST be used
@ -81,7 +81,7 @@ fn main() {
}
```
🌟🌟 Ignoring remaining parts of the value with `..`
5. 🌟🌟 Ignoring remaining parts of the value with `..`
```rust,editable
// fill the blank to make the code work