C++ - Overload templated class method with a partial specilization of that method

Question

There are a few questions already similar to this already on stack overflow, but nothing that seemd to directly answer the question I have. I do apologise if I am reposting.

I'd like to overload a few methods of a templated class (with 2 template parameters) with a partial template specialisation of those methods. I haven't been able to figure out the correct syntax, and am starting to think that it's not possible. I thought I'd post here to see if I can get confirmation.

Example code to follow:

template <typename T, typename U>
class Test
{
public:
    void Set( T t, U u ); 

    T m_T;
    U m_U;
};

// Fully templated method that should be used most of the time
template <typename T, typename U>
inline void Test<T,U>::Set( T t, U u )
{
    m_T=t;
    m_U=u;
}

// Partial specialisation that should only be used when U is a float.
// This generates compile errors
template <typename T>
inline void Test<T,float>::Set( T t, float u )
{
    m_T=t;
    m_U=u+0.5f;
}


int _tmain(int argc, _TCHAR* argv[])
{
    Test<int, int> testOne;    
    int a = 1;
    testOne.Set( a, a );

    Test<int, float> testTwo;    
    float f = 1.f;
    testTwo.Set( a, f );
}

I know that I could write a partial specialisation of the entire class, but that kinda sucks. Is something like this possible?

(I'm using VS2008) Edit: Here is the compile error error C2244: 'Test::Set' : unable to match function definition to an existing declaration

Thanks :)

Answer 1

The particular problem you're sketching is easy:

template< class T >
inline T foo( T const& v ) { return v; }

template<>
float foo( float const& v ) { return v+0.5; }

Then call foo from your Test::Set implementation.

If you want the full generality, then similarly use a helper class with static helper member functions, and partially specialize that helper class.

Cheers & hth.,