non-virtual functions declared in class with virtual functions

[Yadrif]

What are the two non-virtual functions

bool operator ==(const DerivedFromSomeInterfaceIF& right) const
bool operator !=(const SomeInterfaceIF& rhs) const;

in SomeInterfaceIF class doing, if anything?

There is no cooresponding .cpp file with any implementation for them. I don't get what the purpose of these are since they are not marked as pure virtual and have no implementation. I get no compile errors.

#include <cstdlib>
#include <iostream>

using namespace std;

class SomeInterfaceIF
{
    public:
    
        virtual string getName() = 0;
        virtual string getValue() = 0;

        bool operator ==(const SomeInterfaceIF& rhs) const;
        bool operator !=(const SomeInterfaceIF& rhs) const; 

        virtual ~SomeInterfaceIF(){};
    
};

class DerivedFromSomeInterfaceIF : public SomeInterfaceIF
{
    public:
        virtual string getName() {
            // do something here            
        }
        virtual string getValue() {
            // do something here            
        }

        bool operator ==(const DerivedFromSomeInterfaceIF& right) const {
            // do something here
        }
        bool operator !=(const DerivedFromSomeInterfaceIF& right) const {
            // do something here            
        }          

    private:
        string thename;
        string thevalue;
};

int main(int argc, char *argv[])
{
    DerivedFromSomeInterfaceIF intIf;
    
    system("PAUSE");
    return EXIT_SUCCESS;
}

I'm I correct that the two definitions serve no purpose since they are no marked as pure virtual and no implementation in provided?

Thanks.