book: translate ch03

see #12

Author: changkun

book/en-us/03-runtime.md

@@ -42,17 +42,13 @@
 - [**Chapter 03 Language Runtime Enhancements**](./03-runtime.md)
     + 3.1 Lambda expression
         + Basics
-            + Value capture
-            + Reference capture
-            + Implicit capture
-            + Expression capture
-        + Generic lambda
+        + Generics
     + 3.2 Function object wrapper
         + std::function
         + std::bind/std::placeholder
     + 3.3 rvalue reference
         + lvalue, rvalue, prvalue, xvalue
-        + rvalue reference & lvalue reference
+        + rvalue reference and lvalue reference
         + Move semantics
         + Perfect forwarding
 - [**Chapter 04 Containers**](./04-containers.md)
@@ -87,7 +83,7 @@
     + 7.4 Condition Variable
     + 7.5 Atomic Operation and Memory Model
         + Atomic Operation
-        + Concistency Model
+        + Consistency Model
         + Memory Orders
 - [**Chapter 08 File System**](./08-filesystem.md)
     + 8.1 Documents and links

book/en-us/toc.md

@@ -317,8 +317,8 @@ void foo() {
 }
 ```
 
-由于 int& 不能引用 double 类型的参数，因此必须产生一个临时值来保存 s 的值，
-从而当 increase() 修改这个临时值时，从而调用完成后 s 本身并没有被修改。
+由于 `int&` 不能引用 `double` 类型的参数，因此必须产生一个临时值来保存 `s` 的值，
+从而当 `increase()` 修改这个临时值时，从而调用完成后 `s` 本身并没有被修改。
 
 第二个问题，为什么常量引用允许绑定到非左值？原因很简单，因为 Fortran 需要。
 

book/zh-cn/03-runtime.md

@@ -41,15 +41,11 @@
       - 强类型枚举
 - [**第 3 章 语言运行期的强化**](./03-runtime.md)
     + 3.1 lambda 表达式
-        + lambda 表达式基础
-            + 值捕获
-            + 引用捕获
-            + 隐式捕获
-            + 表达式捕获
-        + 泛型 lambda
+        + 基础
+        + 泛型
     + 3.2 函数对象包装器
         + std::function
-        + std::bind/std::placeholder
+        + std::bind 和 std::placeholder
     + 3.3 右值引用
         + 左值、右值的纯右值、将亡值、右值
         + 右值引用和左值引用

book/zh-cn/toc.md

@@ -0,0 +1,61 @@
+//
+// 3.1.lambda.basic.cpp
+// chapter 03 runtime enhancement
+// modern c++ tutorial
+//
+// created by changkun at changkun.de
+// https://github.com/changkun/modern-cpp-tutorial
+//
+
+
+#include <iostream>
+#include <utility>
+
+void lambda_value_capture() {
+    int value = 1;
+    auto copy_value = [value] {
+        return value;
+    };
+    value = 100;
+    auto stored_value = copy_value();
+    std::cout << "stored_value = " << stored_value << std::endl;
+    // At this moment, stored_value == 1, and value == 100.
+    // Because copy_value has copied when its was created.
+}
+
+void lambda_reference_capture() {
+    int value = 1;
+    auto copy_value = [&value] {
+        return value;
+    };
+    value = 100;
+    auto stored_value = copy_value();
+    std::cout << "stored_value = " << stored_value << std::endl;
+    // At this moment, stored_value == 100, value == 100.
+    // Because copy_value stores reference
+}
+
+void lambda_expression_capture() {
+    auto important = std::make_unique<int>(1);
+    auto add = [v1 = 1, v2 = std::move(important)](int x, int y) -> int {
+        return x+y+v1+(*v2);
+    };
+    std::cout << add(3,4) << std::endl;
+}
+
+void lambda_generic() {
+    auto generic = [](auto x, auto y) {
+        return x+y;
+    };
+    
+    std::cout << generic(1, 2) << std::endl;
+    std::cout << generic(1.1, 2.2) << std::endl;
+}
+
+int main() {
+    lambda_value_capture();
+    lambda_reference_capture();
+    lambda_expression_capture();
+    lambda_generic();
+    return 0;
+}

code/3/3.1.cpp

@@ -1,16 +1,16 @@
 //
-// 3.2.cpp
+// 3.2.function.wrap.cpp
+// chapter 03 runtime enhancement
 // modern c++ tutorial
 //
 // created by changkun at changkun.de
 // https://github.com/changkun/modern-cpp-tutorial
 //
-// std::function std::bind
 
 #include <functional>
 #include <iostream>
 
-using foo = void(int);  // 定义函数指针
+using foo = void(int);  // function pointer
 void functional(foo f) {
     f(1);
 }
@@ -24,29 +24,28 @@ int foo3(int a, int b, int c) {
 }
 
 int main() {
-    
+
     auto f = [](int value) {
         std::cout << value << std::endl;
     };
-    functional(f);  // 函数指针调用
-    f(1);           // lambda 表达式调用
-    
-    // std::function 包装了一个返回值为 int, 参数为 int 的函数
+    functional(f);  // call by function pointer
+    f(1);           // call by lambda expression
+
+    // std::function wraps a function that take int paremeter and returns int value
     std::function<int(int)> func = foo2;
-    
+
     int important = 10;
     std::function<int(int)> func2 = [&](int value) -> int {
         return 1+value+important;
     };
     std::cout << func(10) << std::endl;
     std::cout << func2(10) << std::endl;
-    
-    
-    // 将参数1,2绑定到函数 foo 上，但是使用 std::placeholders::_1 来对第一个参数进行占位
+
+    // bind parameter 1, 2 on function foo, and use std::placeholders::_1 as placeholder
+    // for the first parameter.
     auto bindFoo = std::bind(foo3, std::placeholders::_1, 1,2);
-    // 这时调用 bindFoo 时，只需要提供第一个参数即可
+    // when call bindFoo, we only need one param left
     bindFoo(1);
-    
-    
+
     return 0;
 }

code/3/3.1.lambda.basic.cpp

@@ -0,0 +1,38 @@
+//
+// 3.3.rvalue.cpp
+// modern c++ tutorial
+//
+// created by changkun at changkun.de
+// https://github.com/changkun/modern-cpp-tutorial
+//
+
+
+#include <iostream>
+#include <string>
+
+void reference(std::string& str) {
+    std::cout << "lvalue" << std::endl;
+}
+void reference(std::string&& str) {
+    std::cout << "rvalue" << std::endl;
+}
+
+int main()
+{
+    std::string  lv1 = "string,";       // lv1 is a lvalue
+    // std::string&& r1 = s1;           // illegal, rvalue can't ref to lvalue
+    std::string&& rv1 = std::move(lv1); // legal, std::move can convert lvalue to rvalue
+    std::cout << rv1 << std::endl;      // string,
+    
+    const std::string& lv2 = lv1 + lv1; // legal, const lvalue reference can extend temp variable's lifecycle
+    // lv2 += "Test";                   // illegal, const ref can't be modified
+    std::cout << lv2 << std::endl;      // string,string
+    
+    std::string&& rv2 = lv1 + lv2;      // legal, rvalue ref extend lifecycle
+    rv2 += "string";                    // legal, non-const reference can be modified
+    std::cout << rv2 << std::endl;      // string,string,string,
+    
+    reference(rv2);                     // output: lvalue
+    
+    return 0;
+}

code/3/3.2.cpp code/3/3.2.function.wrap.cppcode/3/3.2.cpp renamed to code/3/3.2.function.wrap.cpp

@@ -0,0 +1,16 @@
+//
+// 3.4.historical.cpp
+// modern c++ tutorial
+//
+// created by changkun at changkun.de
+// https://github.com/changkun/modern-cpp-tutorial
+//
+
+#include <iostream>
+
+int main() {
+    // int &a = std::move(1); // illegal, non-const lvalue reference cannot ref rvalue
+    const int &b = std::move(1); // legal, const lvalue reference can
+
+    std::cout << b << std::endl;
+}