fix errors in enum.md

src/pattern-match/intro.md

@@ -1 +1,6 @@
 # Pattern Match
+Learning resources: 
+- English: [Rust Book 18](https://doc.rust-lang.org/book/ch18-00-patterns.html)
+- 简体中文: [Rust语言圣经 - 模式匹配](https://course.rs/basic/match-pattern/intro.html)
+
+

src/pattern-match/match-iflet.md

@@ -1 +1,119 @@
 # match, if let
+
+### match
+🌟🌟
+```rust,editable
+
+// fill the blanks
+enum Direction {
+    East,
+    West,
+    North,
+    South,
+}
+
+fn main() {
+    let dire = Direction::South;
+    match dire {
+        Direction::East => println!("East"),
+        __  => { // matching South or North here
+            println!("South or North");
+        },
+        _ => println!(__),
+    };
+}
+```
+
+🌟🌟 match is an expression, so we can use it in assignments
+```rust,editable
+
+fn main() {
+    let boolean = true;
+
+    // fill the blank with an match expression:
+    //
+    // boolean = true, binary = 1
+    // boolean = false, binary = 0
+    let binary = __;
+
+    assert_eq!(binary, 1);
+}
+```
+
+🌟🌟 using match to get the data an enum variant holds
+```rust,editable
+
+// fill in the blanks
+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 {
+        __ => { // matches  Message::Move
+            assert_eq!(a, 1);
+            assert_eq!(b, 3);
+        },
+        Message::ChangeColor(_, g, b) => {
+            assert_eq!(g, __);
+            assert_eq!(b, __);
+        }
+        __ => println!("no data in these variants")
+    }
+}
+```
+
+### matches!
+[`matches!`](https://doc.rust-lang.org/stable/core/macro.matches.html) looks like `match`, but can do something different
+
+🌟🌟
+```rust,editable
+
+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!(__)
+    }
+} 
+```
+
+🌟🌟
+```rust,editable
+
+enum MyEnum {
+    Foo,
+    Bar
+}
+
+fn main() {
+    let mut count = 0;
+
+    let v = vec![MyEnum::Foo,MyEnum::Bar,MyEnum::Foo];
+    for e in v {
+        if e == MyEnum::Foo { // fix the error with changing only this line
+            count += 1;
+        }
+    }
+
+    assert_eq!(count, 2);
+}
+```
+
+### if let