Public Function Add( _
    ByVal real As Double, _
    ByVal imaginary As Double _
) As 

public IAgCRComplex Add(
    double real,
    double imaginary
);

public: IAgCRComplex^ Add(
    double real,
    double imaginary
);

public IAgCRComplex add(
    double real,
    double imaginary
);

public: HRESULT Add(
    double real,
    double imaginary,
    IAgCRComplex ** ppRetVal
);