Re: Template<void>

Tom Widmer <>
24 Apr 2006 16:17:37 -0400
Allan W wrote:

The name "callbackbase" is used for the base class,
just to factor out the non-template parts. Other than that
it is never used. I wondered if we couldn't use an
otherwise-unused version of the template instead. Is this
legal (or could it be made legal with relatively few changes)?

(Untested code):

template < class T >
class callback;

class callback<void> {
    virtual void operator()() const { };
    virtual ~callback() = 0;
callback<void>::~callback() { }

template < class T >
class callback : public callback<void> {
    typedef void (T::*Func)();
    callback( T& t, Func func ) : object(&t), f(func) { }
    void operator()() const { (object->*f)(); }
    T* object;
    Func f;

Looks perfectly legal to me. There's nothing stopping you deriving the
general template from an explicit or partial specialization. The
principle of least surprise is the only thing against it.


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