add zh-CN/enum.md

deploy.sh

@@ -21,5 +21,5 @@ git remote add origin https://github.com/sunface/rust-by-practice
 git push -u -f origin gh-pages
 
 ## deploy zh-CN
-cd ./zh-CN
+cd ../zh-CN 
 ./deploy

zh-CN/src/compound-types/enum.md

@@ -1 +1,200 @@
-# enum
+# 枚举 Enum
+🌟🌟 在创建枚举时，你可以使用显式的整数设定枚举成员的值。
+
+```rust,editable
+
+// 修复错误
+enum Number {
+    Zero,
+    One,
+    Two,
+}
+
+enum Number1 {
+    Zero = 0,
+    One,
+    Two,
+}
+
+// C语言风格的枚举定义
+enum Number2 {
+    Zero = 0.0,
+    One = 1.0,
+    Two = 2.0,
+}
+
+
+fn main() {
+    // 通过 `as` 可以将枚举值强转为整数类型
+    assert_eq!(Number::One, Number1::One);
+    assert_eq!(Number1::One, Number2::One);
+} 
+```
+
+🌟 枚举成员可以持有各种类型的值
+```rust,editable
+
+// 填空
+enum Message {
+    Quit,
+    Move { x: i32, y: i32 },
+    Write(String),
+    ChangeColor(i32, i32, i32),
+}
+
+fn main() {
+    let msg1 = Message::Move{__}; // 使用x = 1, y = 2 来初始化
+    let msg2 = Message::Write(__); // 使用 "hello, world!" 来初始化
+} 
+```
+
+🌟🌟🌟 枚举成员中的值可以使用模式匹配来获取
+```rust,editable
+
+// 仅填空，不要修改其它代码！
+enum Message {
+    Quit,
+    Move { x: i32, y: i32 },
+    Write(String),
+    ChangeColor(i32, i32, i32),
+}
+
+fn main() {
+    let msg = Message::Move{x: 1, y: 1};
+
+    if let Message::Move{__} = msg {
+        assert_eq!(x, y);
+    }
+
+    panic!("不要让这行代码运行！");
+} 
+```
+
+🌟🌟🌟 使用枚举对类型进行同一化
+
+```rust,editable
+
+// 填空，并修复错误
+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) {
+    println!("{}", msg);
+}
+```
+
+🌟🌟 Rust 中没有 `null`，我们通过 `Option<T>` 枚举来处理值为空的情况
+```rust,editable
+
+// 仅填空，不要修改其它代码！
+fn main() {
+    let five = Some(5);
+    let six = plus_one(five);
+    let none = plus_one(None);
+
+    if let __ = six {
+        println!("{}", n)
+    }
+
+    panic!("不要让这行代码运行！");
+} 
+
+fn plus_one(x: Option<i32>) -> Option<i32> {
+    match x {
+        __ => None,
+        __ => Some(i + 1),
+    }
+}
+```
+
+### 示例
+使用枚举来实现链表.
+
+```rust,editable
+
+use crate::List::*;
+
+enum List {
+    // Cons: Tuple struct that wraps an element and a pointer to the next node
+    Cons(u32, Box<List>),
+    // Nil: A node that signifies the end of the linked list
+    Nil,
+}
+
+// Methods can be attached to an enum
+impl List {
+    // Create an empty list
+    fn new() -> List {
+        // `Nil` has type `List`
+        Nil
+    }
+
+    // Consume a list, and return the same list with a new element at its front
+    fn prepend(self, elem: u32) -> List {
+        // `Cons` also has type List
+        Cons(elem, Box::new(self))
+    }
+
+    // Return the length of the list
+    fn len(&self) -> u32 {
+        // `self` has to be matched, because the behavior of this method
+        // depends on the variant of `self`
+        // `self` has type `&List`, and `*self` has type `List`, matching on a
+        // concrete type `T` is preferred over a match on a reference `&T`
+        // after Rust 2018 you can use self here and tail (with no ref) below as well,
+        // rust will infer &s and ref tail. 
+        // See https://doc.rust-lang.org/edition-guide/rust-2018/ownership-and-lifetimes/default-match-bindings.html
+        match *self {
+            // Can't take ownership of the tail, because `self` is borrowed;
+            // instead take a reference to the tail
+            Cons(_, ref tail) => 1 + tail.len(),
+            // Base Case: An empty list has zero length
+            Nil => 0
+        }
+    }
+
+    // Return representation of the list as a (heap allocated) string
+    fn stringify(&self) -> String {
+        match *self {
+            Cons(head, ref tail) => {
+                // `format!` is similar to `print!`, but returns a heap
+                // allocated string instead of printing to the console
+                format!("{}, {}", head, tail.stringify())
+            },
+            Nil => {
+                format!("Nil")
+            },
+        }
+    }
+}
+
+fn main() {
+    // Create an empty linked list
+    let mut list = List::new();
+
+    // Prepend some elements
+    list = list.prepend(1);
+    list = list.prepend(2);
+    list = list.prepend(3);
+
+    // Show the final state of the list
+    println!("linked list has length: {}", list.len());
+    println!("{}", list.stringify());
+}
+```