Re: Partial template class specialization?

Victor Bazarov <v.bazarov@comcast.invalid>
Tue, 29 Mar 2011 16:08:45 -0400
On 3/29/2011 3:49 PM, MikeWhy wrote:

Victor Bazarov wrote:

On 3/29/2011 1:18 PM, MikeWhy wrote:

I want to override a template class method on a formal parameter. Is
this possible without redefining everything else in the class? The
alternative is a "conditional is constant" warning. For example, call
Reset() only when AutoReset is true:

template <bool AutoReset, class T>
class TimerNode {
void OnTimer();
void DoCall();
template <class T>
void TimerNode<true, T>::OnTimer()
template <class T>
void TimerNode<false, T>::OnTimer()
{ DoCall();

Why do you think you need this dance? Is "Reset" name not available
when 'TimerNode' is instantiated with 'AutoReset==false'? If it is
available all the time, just do

template<bool AR, class T> void TimerNode<AR,T>::OnTimer()
if (AR) Reset();

IOW, why create a problem for yourself where there isn't one?

The compiler should optimize away the conditional for this simple case,
of course. But it isn't difficult to imagine it useful for something
other than a boolean. Specializing on just one or a few typename Foo
rather than the bool here would be the use case. I'll be darned if I can
contrive an example this moment, though.

You would have to partially specialise the entire template in that case.
  Or you could define a helper template (class or function). The
specifics of the solution depend on the problem, of course.

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