show the importance of member initializer lists

lectures/25_inheritance/constructor_test1.cpp

@@ -0,0 +1,18 @@
+#include <iostream>
+
+class Base {
+public:
+    Base(int x) {
+        std::cout << "Base constructor: " << x << std::endl;
+    }
+};
+
+class Derived : public Base {
+public:
+    Derived(int x) : Base(x) { // member initializer list calls Base constructor
+        std::cout << "Derived constructor" << std::endl;
+    }
+};
+
+int main(){
+}