book: translation of ch04

Update #12

code/4/4.1.cpp

@@ -1,36 +0,0 @@
-//
-// 4.1.cpp
-// modern c++ tutorial
-//
-// created by changkun at changkun.de
-// https://github.com/changkun/modern-cpp-tutorial
-//
-// std::array
-
-#include <iostream>
-#include <array>
-
-void foo(int *p, int len) {
-    for (int i = 0; i != len; ++i) {
-        std::cout << p[i] << std::endl;
-    }
-}
-
-int main() {
-    std::array<int, 4> arr= {1,4,3,2};
-    
-    //int len = 4;
-    //std::array<int, len> arr = {1,2,3,4}; // 非法, 数组大小参数必须是常量表达式
-    
-    // C 风格接口传参
-    // foo(arr, arr.size());           // 非法, 无法隐式转换
-    foo(&arr[0], arr.size());
-    foo(arr.data(), arr.size());
-    
-    // 更多接口使用
-    std::sort(arr.begin(), arr.end());
-    for(auto &i : arr)
-        std::cout << i << std::endl;
-    
-    return 0;
-}

code/4/4.1.linear.container.cpp

@@ -0,0 +1,68 @@
+//
+// 4.1.linear.container.cpp
+// modern c++ tutorial
+//
+// created by changkun at changkun.de
+// https://github.com/changkun/modern-cpp-tutorial
+//
+
+#include <iostream>
+#include <array>
+#include <vector>
+
+void foo(int *p, int len) {
+    for (int i = 0; i != len; ++i) {
+        std::cout << p[i] << std::endl;
+    }
+}
+
+int main() {
+    std::vector<int> v;
+    std::cout << "size:" << v.size() << std::endl;         // output 0
+    std::cout << "capacity:" << v.capacity() << std::endl; // output 0
+
+    // As you can see, the storage of std::vector is automatically managed and 
+    // automatically expanded as needed.
+    // But if there is not enough space, you need to redistribute more memory, 
+    // and reallocating memory is usually a performance-intensive operation.
+    v.push_back(1);
+    v.push_back(2);
+    v.push_back(3);
+    std::cout << "size:" << v.size() << std::endl;         // output 3
+    std::cout << "capacity:" << v.capacity() << std::endl; // output 4
+
+    // The auto-expansion logic here is very similar to Golang's slice.
+    v.push_back(4);
+    v.push_back(5);
+    std::cout << "size:" << v.size() << std::endl;         // output 5
+    std::cout << "capacity:" << v.capacity() << std::endl; // output 8
+
+    // As can be seen below, although the container empties the element, 
+    // the memory of the emptied element is not returned.
+    v.clear();                                             
+    std::cout << "size:" << v.size() << std::endl;         // output 0
+    std::cout << "capacity:" << v.capacity() << std::endl; // output 8
+
+    // Additional memory can be returned to the system via the shrink_to_fit() call
+    v.shrink_to_fit();
+    std::cout << "size:" << v.size() << std::endl;         // output 0
+    std::cout << "capacity:" << v.capacity() << std::endl; // output 0
+
+
+    std::array<int, 4> arr= {1,4,3,2};
+    
+    //int len = 4;
+    //std::array<int, len> arr = {1,2,3,4}; // illegal, size of array must be constexpr
+    
+    // C style parameter passing
+    // foo(arr, arr.size());           // illegal, cannot convert implicitly
+    foo(&arr[0], arr.size());
+    foo(arr.data(), arr.size());
+
+    // more usage
+    std::sort(arr.begin(), arr.end());
+    for(auto &i : arr)
+        std::cout << i << std::endl;
+    
+    return 0;
+}

code/4/4.2.unordered.map.cpp

@@ -1,11 +1,11 @@
 //
-// 4.2.cpp
+// 4.2.unordered.map.cpp
+// chapter 04 containers
 // modern c++ tutorial
 //
 // created by changkun at changkun.de
 // https://github.com/changkun/modern-cpp-tutorial
 //
-// 无序容器
 
 #include <iostream>
 #include <string>
@@ -13,7 +13,7 @@
 #include <map>
 
 int main() {
-    // 两组结构按同样的顺序初始化
+    // initialized in same order
     std::unordered_map<int, std::string> u = {
         {1, "1"},
         {3, "3"},
@@ -25,7 +25,7 @@ int main() {
         {2, "2"}
     };
     
-    // 分别对两组结构进行遍历
+    // iterates in the same way
     std::cout << "std::unordered_map" << std::endl;
     for( const auto & n : u)
         std::cout << "Key:[" << n.first << "] Value:[" << n.second << "]\n";

code/4/4.3.tuples.cpp

@@ -1,11 +1,11 @@
 //
-// 4.3.cpp
+// 4.3.tuples.cpp
+// chapter 04 containers
 // modern c++ tutorial
 //
 // created by changkun at changkun.de
 // https://github.com/changkun/modern-cpp-tutorial
 //
-// std::tuple 及其操作
 
 
 #include <tuple>
@@ -15,19 +15,19 @@
 auto get_student(int id)
 {
     if (id == 0)
-        return std::make_tuple(3.8, 'A', "张三");
+        return std::make_tuple(3.8, 'A', "John");
     if (id == 1)
-        return std::make_tuple(2.9, 'C', "李四");
+        return std::make_tuple(2.9, 'C', "Jack");
     if (id == 2)
-        return std::make_tuple(1.7, 'D', "王五");
-    // 返回类型被推断为 std::tuple<double, char, std::string>
+        return std::make_tuple(1.7, 'D', "Ive");
+    // return type is std::tuple<double, char, std::string>
     return std::make_tuple(0.0, 'D', "null");
 }
 
 template <size_t n, typename... T>
 constexpr std::variant<T...> _tuple_index(const std::tuple<T...>& tpl, size_t i) {
     if constexpr (n >= sizeof...(T))
-        throw std::out_of_range("越界.");
+        throw std::out_of_range("out of range.");
     if (i == n)
         return std::variant<T...>{ std::in_place_index<n>, std::get<n>(tpl) };
     return _tuple_index<(n < sizeof...(T)-1 ? n+1 : 0)>(tpl, i);
@@ -52,32 +52,32 @@ int main()
 {
     auto student = get_student(0);
     std::cout << "ID: 0, "
-    << "GPA: " << std::get<0>(student) << ", "
-    << "成绩: " << std::get<1>(student) << ", "
-    << "姓名: " << std::get<2>(student) << '\n';
+              << "GPA: "   << std::get<0>(student) << ", "
+              << "Grade: " << std::get<1>(student) << ", "
+              << "Name: "  << std::get<2>(student) << '\n';
     
     double gpa;
     char grade;
     std::string name;
     
-    // 元组进行拆包
+    // tuple unpack
     std::tie(gpa, grade, name) = get_student(1);
     std::cout << "ID: 1, "
-    << "GPA: " << gpa << ", "
-    << "成绩: " << grade << ", "
-    << "姓名: " << name << '\n';
+              << "GPA: "   << gpa   << ", "
+              << "Grade: " << grade << ", "
+              << "Name: "  << name  << '\n';
     
     
     std::tuple<std::string, double, double, int> t("123", 4.5, 6.7, 8);
     std::cout << std::get<std::string>(t) << std::endl;
-    // std::cout << std::get<double>(t) << std::endl;   // 非法, 引发编译期错误
+    // std::cout << std::get<double>(t) << std::endl;   // illegal, runtime error
     std::cout << std::get<3>(t) << std::endl;
     
-    // 拼接元组
+    // concat
     auto new_tuple = std::tuple_cat(get_student(1), std::move(t));
     
-    // 迭代
+    // iteration
     for(int i = 0; i != tuple_len(new_tuple); ++i) {
-        std::cout << tuple_index(new_tuple, i) << std::endl; // 运行期索引
+        std::cout << tuple_index(new_tuple, i) << std::endl; // runtime indexing
     }
 }

code/4/Makefile

@@ -0,0 +1,14 @@
+#
+# modern cpp tutorial
+#
+# created by changkun at changkun.de
+# https://github.com/changkun/modern-cpp-tutorial
+#
+
+all: $(patsubst %.cpp, %.out, $(wildcard *.cpp))
+
+%.out: %.cpp Makefile
+	clang++ $< -o $@ -std=c++2a -pedantic
+
+clean:
+	rm *.out