book: translation of ch04

Update #12

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;
+}