Remove unused code and migrate to CMake build system.

cpp/classes/CMakeLists.txt

@@ -0,0 +1,6 @@
+cmake_minimum_required(VERSION 4.1)
+project(pointer)
+
+set(CMAKE_CXX_STANDARD 20)
+
+add_executable(pointer main.cpp ClassA.cpp)

cpp/classes/ClassA.cpp

@@ -0,0 +1,11 @@
+#include "ClassA.h"
+
+#include <iostream>
+
+void ClassA::Print() {
+    std::cout << "ClassA" << std::endl;
+}
+
+int ClassA::CompareTo(IComparable *other) {
+    return 0;
+}

cpp/classes/ClassA.h

@@ -0,0 +1,23 @@
+#ifndef POINTER_CLASSA_H
+#define POINTER_CLASSA_H
+#include "IComparable.h"
+
+
+class ClassA : public IComparable {
+// private
+
+public:
+    // public
+    void Print();
+    int CompareTo(IComparable* other) override;
+
+protected:
+    // protected
+
+private:
+    // private
+    int _number = 0;
+};
+
+
+#endif //POINTER_CLASSA_H

cpp/classes/IComparable.h

@@ -0,0 +1,9 @@
+#ifndef POINTER_ICOMPARABLE_H
+#define POINTER_ICOMPARABLE_H
+
+class IComparable {
+public:
+    virtual int CompareTo(IComparable* other) = 0;
+};
+
+#endif //POINTER_ICOMPARABLE_H

cpp/classes/main.cpp

@@ -0,0 +1,24 @@
+#include "ClassA.h"
+
+int main() {
+    ClassA a{};
+    a.Print();
+
+    ClassA *pA = nullptr;
+    pA = new ClassA();
+    pA->Print();
+    // (*pA).Print(); // same line as above, but more complex to write
+    delete pA;
+    pA = nullptr;
+
+    a.CompareTo(pA);
+
+    IComparable *pComparable = nullptr;
+    pComparable = new ClassA();
+    pComparable->CompareTo(pA);
+    // pA = dynamic_cast<ClassA *>(pComparable);
+    delete pComparable;
+    pComparable = nullptr;
+
+    return 0;
+}