From 5807a3147d2d15439ed1ce509cca9360738504f6 Mon Sep 17 00:00:00 2001
From: sunface <cto@188.com>
Date: Wed, 2 Mar 2022 21:59:22 +0800
Subject: [PATCH] add solutions for match.md

---
 solutions/pattern-match/match.md | 168 +++++++++++++++++++++++++++++++
 src/pattern-match/match-iflet.md |  18 ++--
 2 files changed, 177 insertions(+), 9 deletions(-)

diff --git a/solutions/pattern-match/match.md b/solutions/pattern-match/match.md
index e69de29..8910145 100644
--- a/solutions/pattern-match/match.md
+++ b/solutions/pattern-match/match.md
@@ -0,0 +1,168 @@
+1.
+```rust
+enum Direction {
+    East,
+    West,
+    North,
+    South,
+}
+
+fn main() {
+    let dire = Direction::South;
+    match dire {
+        Direction::East => println!("East"),
+        Direction::South | Direction::North  => { // matching South or North here
+            println!("South or North");
+        },
+        _ => println!("West"),
+    };
+}
+```
+
+2.
+```rust
+fn main() {
+    let boolean = true;
+
+    // fill the blank with an match expression:
+    //
+    // boolean = true => binary = 1
+    // boolean = false =>  binary = 0
+    let binary = match boolean {
+        true => 1,
+        false => 0
+    };
+
+    assert_eq!(binary, 1);
+}
+```
+
+3.
+```rust
+enum Message {
+    Quit,
+    Move { x: i32, y: i32 },
+    Write(String),
+    ChangeColor(i32, i32, i32),
+}
+
+fn main() {
+    let msgs = [
+        Message::Quit,
+        Message::Move{x:1, y:3},
+        Message::ChangeColor(255,255,0)
+    ];
+
+    for msg in msgs {
+        show_message(msg)
+    }
+} 
+
+fn show_message(msg: Message) {
+    match msg {
+        Message::Move{x: a, y: b} => { // match  Message::Move
+            assert_eq!(a, 1);
+            assert_eq!(b, 3);
+        },
+        Message::ChangeColor(_, g, b) => {
+            assert_eq!(g, 255);
+            assert_eq!(b, 0);
+        }
+        __ => println!("no data in these variants")
+    }
+}
+```
+
+4.
+```rust
+fn main() {
+    let alphabets = ['a', 'E', 'Z', '0', 'x', '9' , 'Y'];
+
+    // fill the blank with `matches!` to make the code work
+    for ab in alphabets {
+        assert!(matches!(ab, 'a'..='z' | 'A'..='Z' | '0' | '9'))
+    }
+} 
+```
+
+5.
+```rust
+enum MyEnum {
+    Foo,
+    Bar
+}
+
+fn main() {
+    let mut count = 0;
+
+    let v = vec![MyEnum::Foo,MyEnum::Bar,MyEnum::Foo];
+    for e in v {
+        if matches!(e , MyEnum::Foo) { // fix the error with changing only this line
+            count += 1;
+        }
+    }
+
+    assert_eq!(count, 2);
+}
+```
+
+6.
+```rust
+fn main() {
+    let o = Some(7);
+
+    if let Some(i) = o {
+        println!("This is a really long string and `{:?}`", i);
+    }
+}
+```
+
+7.
+```rust
+enum Foo {
+    Bar(u8)
+}
+
+fn main() {
+    let a = Foo::Bar(1);
+
+    if let Foo::Bar(i) = a {
+        println!("foobar holds the value: {}", i);
+    }
+}
+```
+
+8.
+```rust
+enum Foo {
+    Bar,
+    Baz,
+    Qux(u32)
+}
+
+fn main() {
+    let a = Foo::Qux(10);
+
+    match a {
+        Foo::Bar => println!("match foo::bar"),
+        Foo::Baz => println!("match foo::baz"),
+        _ =>  println!("match others")
+    }
+}
+```
+
+9.
+```rust
+fn main() {
+    let age = Some(30);
+    if let Some(age) = age { // create a new variable with the same name as previous `age`
+       assert_eq!(age, 30);
+    } // the new variable `age` goes out of scope here
+    
+    match age {
+        // match can also introduce a new shadowed variable
+        Some(age) =>  println!("age is a new variable, it's value is {}",age),
+        _ => ()
+    }
+ }
+```
\ No newline at end of file
diff --git a/src/pattern-match/match-iflet.md b/src/pattern-match/match-iflet.md
index a4dc682..2ed54eb 100644
--- a/src/pattern-match/match-iflet.md
+++ b/src/pattern-match/match-iflet.md
@@ -1,7 +1,7 @@
 # match, if let
 
 ### match
-🌟🌟
+1. 🌟🌟
 ```rust,editable
 
 // fill the blanks
@@ -24,7 +24,7 @@ fn main() {
 }
 ```
 
-🌟🌟 match is an expression, so we can use it in assignments
+2. 🌟🌟 match is an expression, so we can use it in assignments
 ```rust,editable
 
 fn main() {
@@ -40,7 +40,7 @@ fn main() {
 }
 ```
 
-🌟🌟 using match to get the data an enum variant holds
+3. 🌟🌟 using match to get the data an enum variant holds
 ```rust,editable
 
 // fill in the blanks
@@ -81,7 +81,7 @@ fn show_message(msg: Message) {
 ### matches!
 [`matches!`](https://doc.rust-lang.org/stable/core/macro.matches.html) looks like `match`, but can do something different
 
-🌟🌟
+4. 🌟🌟
 ```rust,editable
 
 fn main() {
@@ -94,7 +94,7 @@ fn main() {
 } 
 ```
 
-🌟🌟
+5. 🌟🌟
 ```rust,editable
 
 enum MyEnum {
@@ -119,7 +119,7 @@ fn main() {
 ### if let
 For some cases, when matching enums, `match` is too heavy, we can use `if let` instead.
 
-🌟 
+6. 🌟 
 ```rust,editable
 
 fn main() {
@@ -135,7 +135,7 @@ fn main() {
 }
 ```
 
-🌟🌟
+7. 🌟🌟
 ```rust,editable
 
 // fill in the blank
@@ -152,7 +152,7 @@ fn main() {
 }
 ```
 
-🌟🌟
+8. 🌟🌟
 ```rust,editable
 
 enum Foo {
@@ -176,7 +176,7 @@ fn main() {
 ```
 
 ### Shadowing
-🌟🌟
+9. 🌟🌟
 ```rust,editable
 
 // fix the errors in-place