Friends, operator keyword and scope resolution

Question

namespace GameForge
{
    namespace Core
    {
        class CTribool;
    }
}

GameForge::Core::CTribool operator ! ( const GameForge::Core::CTribool& rkTribool );

namespace GameForge
{
    namespace Core
    {
        class CTribool
        {
            friend CTribool operator ! ( const CTribool& rkTribool );

        private:
            EState m_eState;
        };
    }
}


GameForge::Core::CTribool operator ! ( const GameForge::Core::CTribool& rkTribool )
{
    switch( rkTribool.m_eState )
        {
    // Some stuff...

Does not compile because m_eState is not accessible within the last definition. The reason is that the friend declaration occurs in the CTribool namespace and thus declares a different function. So i tried to use scope resolution operator as follow.

friend CTribool ::operator ! ( const CTribool& rkTribool );

and

friend CTribool ::( operator ! ) ( const CTribool& rkTribool );

But that doesn't work either because somehow CTribool is not recognized as a valid type. I suspect that the forward declaration is not enough in this case. Any work around ?

Answer 1

Strangely enough, you need to do this:

        friend CTribool (::operator !) ( const CTribool& rkTribool );

You need to specify that your function is in global scope, but without the parentheses, your :: would bind with CTribool, as if you were doing this:

        friend (CTribool::operator !) ( const CTribool& rkTribool );

in which case it would think you were specifying a function without a return type.

Answer 2

You should define your operator in the same namespace as you define the CTribool class. It's the right way to do it; it will be found during application by ADL:

namespace GameForge
{
    namespace Core
    {
        class CTribool
        {
            friend CTribool operator ! ( const CTribool& rkTribool );

        private:
            EState m_eState;
        };
    }
}



namespace GameForge
{
    namespace Core
    {
        CTribool operator ! ( const GameForge::Core::CTribool& rkTribool )
        {
            switch( rkTribool.m_eState )
                {
                // Some stuff...
                }
        }
    }
}