add zh/as.md

src/type-conversions/as.md

@@ -1,4 +1,4 @@
-# Type Conversions
+# Convert by `as`
 Rust provides no implicit type conversion(coercion) between primitive types. But explicit type conversions can be performed using the `as` keyword.
 
 1. 🌟
@@ -89,7 +89,7 @@ fn main() {
 ```
 
 
-5. 🌟🌟🌟
+5. 🌟🌟🌟 
 ```rust,editable
 fn main() {
     let arr :[u64; 13] = [0; 13];

zh-CN/src/type-conversions/as.md

@@ -1,10 +1,10 @@
-# Type Conversions
-Rust provides no implicit type conversion(coercion) between primitive types. But explicit type conversions can be performed using the `as` keyword.
+# 使用 as 进行类型转换
+Rust 并没有为基本类型提供隐式的类型转换( coercion )，但是我们可以通过 `as` 来进行显式地转换。
 
 1. 🌟
 ```rust,editable
-// FIX the errors and FILL in the blank
-// DON'T remove any code
+// 修复错误，填空
+// 不要移除任何代码
 fn main() {
     let decimal = 97.123_f32;
 
@@ -19,43 +19,42 @@ fn main() {
 }
 ```
 
-2. 🌟🌟 By default, overflow will cause compile errors, but we can add an global annotation to suppress these errors.
+2. 🌟🌟 默认情况下, 数值溢出会导致编译错误，但是我们可以通过添加一行全局注解的方式来避免编译错误(溢出还是会发生)
 ```rust,editable
 fn main() {
     assert_eq!(u8::MAX, 255);
-    // the max of `u8` is 255 as shown above.
-    // so the below code will cause an overflow error: literal out of range for `u8`.
-    // PLEASE looking for clues within compile errors to FIX it.
-    // DON'T modify any code in main.
+    // 如上所示，u8 类型允许的最大值是 255.
+    // 因此以下代码会报溢出的错误： literal out of range for `u8`.
+    // **请仔细查看相应的编译错误，从中寻找到解决的办法**
+    // **不要修改 main 中的任何代码**
     let v = 1000 as u8;
 
     println!("Success!")
 }
 ```
 
-3. 🌟🌟  when casting any value to an unsigned type `T`, `T::MAX + 1` is added or subtracted until the value fits into the new type.
+3. 🌟🌟  当将任何数值转换成无符号整型 `T` 时，如果当前的数值不在新类型的范围内，我们可以对当前数值进行加值或减值操作( 增加或减少 `T::MAX + 1` )，直到最新的值在新类型的范围内，假设我们要将 `300` 转成 `u8` 类型，由于`u8` 最大值是 255，因此 `300` 不在新类型的范围内并且大于新类型的最大值，因此我们需要减去 `T::MAX + 1`，也就是 `300` - `256` = `44`。
+
 ```rust,editable
 fn main() {
     assert_eq!(1000 as u16, __);
 
     assert_eq!(1000 as u8, __);
 
-    // For positive numbers, this is the same as the modulus
+    // 事实上，之前说的规则对于正整数而言，就是如下的取模
     println!("1000 mod 256 is : {}", 1000 % 256);
 
     assert_eq!(-1_i8 as u8, __);
     
-    // Since Rust 1.45, the `as` keyword performs a *saturating cast* 
-    // when casting from float to int. If the floating point value exceeds 
-    // the upper bound or is less than the lower bound, the returned value 
-    // will be equal to the bound crossed.
+
+    // 从 Rust 1.45 开始，当浮点数超出目标整数的范围时，转化会直接取正整数取值范围的最大或最小值
     assert_eq!(300.1_f32 as u8, __);
     assert_eq!(-100.1_f32 as u8, __);
     
 
-    // This behavior incurs a small runtime cost and can be avoided 
-    // with unsafe methods, however the results might overflow and 
-    // return **unsound values**. Use these methods wisely:
+    // 上面的浮点数转换有一点性能损耗，如果大家对于某段代码有极致的性能要求，
+    // 可以考虑下面的方法，但是这些方法的结果可能会溢出并且返回一些无意义的值
+    // 总之，请小心使用
     unsafe {
         // 300.0 is 44
         println!("300.0 is {}", 300.0_f32.to_int_unchecked::<u8>());
@@ -67,18 +66,18 @@ fn main() {
 }
 ```
 
-4. 🌟🌟🌟 Raw pointer can be converted to memory address (integer) and vice versa
+4. 🌟🌟🌟 裸指针可以和代表内存地址的整数互相转换
 ```rust,editable
 
-// FILL in the blanks
+// 填空
 fn main() {
     let mut values: [i32; 2] = [1, 2];
     let p1: *mut i32 = values.as_mut_ptr();
     let first_address: usize = p1 __; 
     let second_address = first_address + 4; // 4 == std::mem::size_of::<i32>()
-    let p2: *mut i32 = second_address __; // p2 points to the 2nd element in values
+    let p2: *mut i32 = second_address __; // p2 指向 values 数组中的第二个元素
     unsafe {
-        // add one to the second element
+        // 将第二个元素加 1
         __
     }
     
@@ -89,7 +88,7 @@ fn main() {
 ```
 
 
-5. 🌟🌟🌟
+1. 🌟🌟🌟 
 ```rust,editable
 fn main() {
     let arr :[u64; 13] = [0; 13];