Template Member function specialization

[Silvermaul]

Hi guys,

I am implementing some rotation algorithm for medical images and I was wondering if it is possible to specialize a member function of a template class depending on the rotation angle. I.e. If the angle is 180 degress then the algorithm is much simpler.

I don't think this is possible if anyone knows different please let me know!

Regards

Silver

[jsmith]

The angle would have to be of an integral type, and the angle would have to be specified at compile time.

class Image {
  public:
    template< int AngleInDegrees >  // <- Note, int
    void rotate()
    {
        // stuff here
    }

    template<>
    void rotate<180>()
    {
        // special implementation
    }
};

Invocation:

Image i1;
i1.rotate<90>();
i1.rotate<180>();

// Note: this won't compile:
int angle = rand() % 361;
i1.rotate<i>();   // Template parameter has to be known at compile time 

[hamsterman]

Template parameters must be known at compile time.
Maybe you could make rotate<180>() work, but not rotate<angle>().
Why not use an if? And why do this at all? The algorithm for rotation is neither complicated nor costly.

[Silvermaul]

Yes I have already implement a rotation algorithm with billinear interpolation and of course I use an if since for 180 degrees the algorith is some loops. My class is a template class since there is no way to know my data format at compile time. It may be unsigned char, unsigned short, unsigned int. Thus the template class. However I was curious whether you can somehow specify a specialization for an integer type. Apparently I was wrong :)