class - Difference between “::” “.” and “->” in c++

Question

I have found the class Kwadrat. The author used three types of operator ::, . and ->. The arrow is the one that only works. What's the difference between those three?

#include <iostream>

using namespace std;

class Kwadrat{
public:
int val1, val2, val3;
    Kwadrat(int val1, int val2, int val3)
    {
        this->val1 = val1;
        //this.val2 = val2;
        //this::val3 = val3;
    }
};

int main()
{
    Kwadrat* kwadrat = new Kwadrat(1,2,3);
    cout<<kwadrat->val1<<endl;
    cout<<kwadrat->val2<<endl;
    cout<<kwadrat->val3<<endl;
    return 0;
}

Answer 1

• :: names a type within a namespace, a variable within a namespace, a static variable in a class, or a type in a class.
• . names an instance variable or member function
• a->b is syntactic sugar for (*a).b.