add variable exercises

Readme.md

@@ -15,9 +15,11 @@ This book is written in English and Chinese, you can pick up the language you ar
 - 简体中文: [https://zh.exercise.rs](https://zh.exercise.rs)
 
 ## About exercises
+- Try your best to make exercise comipile with NO ERRORS!
 - difficulty level: easy: 🌟  medium: 🌟🌟 hard: 🌟🌟🌟  hell: 🌟🌟🌟🌟
 - Everything is online: reading, editing, testing 
 
+
 ## Contributing
 We welcome all kinds of contributors, especially ones who has precious exercises.
 

deploy.sh

@@ -0,0 +1,7 @@
+cd en 
+./deploy
+
+cd ../zh-CN
+./deploy
+
+cd ..

en/src/variables.md

@@ -1 +1,119 @@
 # Variables
+
+### Binding and mutablity
+🌟 fix the error below with least change
+```rust,editable
+
+fn main() {
+    let x: i32; // uninitialized but using, ERROR !
+    let y: i32; // uninitialized but also unusing, only warning
+    println!("{} is equal to 5", x); 
+}
+```
+
+🌟🌟 fill the blanks in code to make it compile
+```rust,editable
+
+fn main() {
+    // replace __ with a variable name
+    let __ =  1;
+    __ += 2; 
+    
+    println!("{} is equal to 3", x); 
+}
+```
+
+### Scope
+🌟 fix the error below with least change
+```rust,editable
+
+fn main() {
+    let x: i32 = 10;
+    {
+        let y: i32 = 5;
+        println!("The value of x is {} and value of y is {}", x, y);
+    }
+    println!("The value of x is {} and value of y is {}", x, y); 
+}
+```
+
+🌟🌟 fix the error with the knowledge you grasped
+```rust,editable
+
+fn main() {
+    println!("{}, world", x); 
+}
+
+fn define_x() {
+    let x = "hello";
+}
+```
+
+### Shadowing
+🌟🌟 only change `assert_eq!` to make the `println!` work(print `42` in terminal)
+
+```rust,editable
+
+fn main() {
+    let x: i32 = 5;
+    {
+        let x = 12;
+        assert_eq!(x, 5);
+    }
+
+    assert_eq!(x, 12);
+
+    let x =  42;
+    println!("{}", x); // Prints "42".
+}
+```
+
+🌟🌟 remove a line in code to make it compile
+```rust,editable
+
+fn main() {
+    let mut x: i32 = 1;
+    x = 7;
+    // shadowing and re-binding
+    let x = x; 
+    x += 3;
+
+
+    let y = 4;
+    // shadowing
+    let y = "I can also be bound to text!"; 
+}
+```
+
+### Unused varibles
+fix the warning below with :
+
+- 🌟  one way
+- 🌟🌟  two ways
+
+> Note: there are two ways you can use, but none of them is removing the line `let x = 1` 
+
+```rust,editable
+
+fn main() {
+    let x = 1; 
+}
+
+// warning: unused variable: `x`
+```
+
+### Destructing
+🌟🌟 fix the error below with least change
+
+> Tips: you can use Shadowing or Mutability
+
+```rust,editable
+
+fn main() {
+    let (x, y) = (1, 2);
+    x += 2;
+
+    assert_eq!(x, 3);
+    assert_eq!(y, 2);
+}
+```

zh-CN/src/SUMMARY.md

@@ -1,7 +1,7 @@
 # Summary
 
 - [关于 exercise.rs](why-exercise.md)
-- [变量绑定与解构 todo](variables.md)
+- [变量绑定与解构](variables.md)
 - [基本类型 todo](basic-types/intro.md)
   - [数值类型](basic-types/numbers.md)
   - [字符、布尔、单元类型](basic-types/char-bool-unit.md)

zh-CN/src/variables.md

@@ -1 +1,120 @@
-# Variables
+# 变量绑定与解构
+
+### 绑定和可变性
+🌟 修复下面代码的错误并尽可能少的修改
+
+```rust,editable
+
+fn main() {
+    let x: i32; // 未初始化，但被使用
+    let y: i32; // 未初始化，也未被使用
+    println!("{} is equal to 5", x); 
+}
+```
+
+🌟🌟 完形填空，让代码编译
+```rust,editable
+
+fn main() {
+    // 使用合适的变量名替代 __ 
+    let __ =  1;
+    __ += 2; 
+    
+    println!("{} = 3", x); 
+}
+```
+
+### 变量作用域
+🌟 修复下面代码的错误并使用尽可能少的改变
+```rust,editable
+
+fn main() {
+    let x: i32 = 10;
+    {
+        let y: i32 = 5;
+        println!("x 的值是 {}, y 的值是 {}", x, y);
+    }
+    println!("x 的值是 {}, y 的值是 {}", x, y); 
+}
+```
+
+🌟🌟 使用你所掌握的知识来修复错误
+```rust,editable
+
+fn main() {
+    println!("{}, world", x); 
+}
+
+fn define_x() {
+    let x = "hello";
+}
+```
+
+### 变量遮蔽( Shadowing )
+🌟🌟 只允许修改 `assert_eq!` 来让 `println!` 工作(在终端输出 `42`)
+
+```rust,editable
+
+fn main() {
+    let x: i32 = 5;
+    {
+        let x = 12;
+        assert_eq!(x, 5);
+    }
+
+    assert_eq!(x, 12);
+
+    let x =  42;
+    println!("{}", x); // 输出 "42".
+}
+```
+
+🌟🌟 删除一行代码以通过编译
+```rust,editable
+
+fn main() {
+    let mut x: i32 = 1;
+    x = 7;
+    // 遮蔽且再次绑定
+    let x = x; 
+    x += 3;
+
+
+    let y = 4;
+    // 遮蔽
+    let y = "I can also be bound to text!"; 
+}
+```
+
+### 未使用的变量
+使用以下方法来修复编译器输出的 warning :
+
+- 🌟  一种方法
+- 🌟🌟  两种方法
+
+> 注意: 你可以使用两种方法解决，但是它们没有一种是移除 `let x = 1` 所在的代码行
+
+```rust,editable
+
+fn main() {
+    let x = 1; 
+}
+
+// compiler warning: unused variable: `x`
+```
+
+### 变量解构
+🌟🌟 修复下面代码的错误并尽可能少的修改
+
+> 提示: 可以使用变量遮蔽或可变性
+
+```rust,editable
+
+fn main() {
+    let (x, y) = (1, 2);
+    x += 2;
+
+    assert_eq!(x, 3);
+    assert_eq!(y, 2);
+}
+```

zh-CN/src/why-exercise.md

@@ -1,4 +1,4 @@
-# Why Exercise.rs
+# 关于 exercise.rs
 > 英文版 [传送门](https://exercise.rs)
 
 欢迎大家来到 `exercise.rs`，在来到这里之前不知道你有没有碰到过以下问题: