Class Type Parameters

[Hans-Eric Grönlund]

> Also, this function would be a great place to use a lazy void parameter for 
> the toTry parameter ;) 

Pardon me for being ignorant, but could you elaborate a little on this subject?



Jarrett Billingsley Wrote:

> "Christopher Wright" <dhasenan at gmail.com> wrote in message 
> news:fn2bqa$25rl$1 at digitalmars.com...
> >
> > Closest you could come, if you really didn't want to use a template, is:
> > void retryable(ClassInfo info, int times, void delegate() totry) {
> >    for (int i = 0; i < times; i++) {
> >        try {
> >           totry();
> >           break;
> >        } catch (Exception e) {
> >           if (e.classinfo is info) continue; else throw e;
> >        }
> >    }
> > }
> >
> > retryable(AbandonedMutexException.classinfo, 5, {writefln("Hi!");});
> 
> The only possible issue I could see with that would be if an exception were 
> thrown that was derived from the type that you passed in, which, according 
> to normal exception behavior, should still be caught.  What you have to do 
> then is perform a dynamic cast.  There's no syntax for this, but you can 
> hack around with some of the runtime functions to do the same thing.  Place:
> 
> extern(C) Object _d_dynamic_cast(Object o, ClassInfo c);
> 
> somewhere in your module, then in the catch clause of retryable:
> 
> catch(Exception e)
> {
>     if(_d_dynamic_cast(e, info))
>         continue;
>     else
>         throw e;
> }
> 
> That _should_ work.  It's doing the same thing as the cast operator would 
> but without the pretty syntax.
> 
> Also, this function would be a great place to use a lazy void parameter for 
> the toTry parameter ;) 
> 
>