Re: [aspectj-dev] if (false) pointcut and the empty set

[Wes Isberg <wes@xxxxxxxxxxxxxx>]

> What about providing syntactic sugar and making empty() ...

Of course, users can do this now, which will help them migrate in
the future:

----

public class LibraryPointcuts {
    pointcut never();
    // and for later?
    // pointcut never() : if(false);
    private LibraryPointcuts() {}
}

----

btw, I prefer "never" to "empty" or "none" b/c thinking in terms
of "sets" of join points matched can be misleading.  Ron I believe
first publicly proposed "never" in

  http://dev.eclipse.org/mhonarc/lists/aspectj-dev/msg00506.html

Wes

Ron Bodkin wrote:
> What about providing syntactic sugar and making empty() be the name for the empty pointcut?
>
> Separately, I think the if(false) request is an optimization. There's a good analogy in Java itself; writing if(false) statement; is almost equivalent to writing nothing too. However, it too imposes some additional constraints on the code that will be optimized away, e.g.,
> if(false) throw new UndeclaredCheckedException("this will be a compiler error");
>
> Ron Bodkin
> Chief Technology Officer
> New Aspects of Security
> m: (415) 509-2895
>
>
> > ------------Original Message-------------
> > From: Jim Hugunin <lists@xxxxxxxxxxx>
> > To: aspectj-dev@xxxxxxxxxxx
> > Date: Fri, Sep-5-2003 8:55 AM
> > Subject: Re: [aspectj-dev] if (false) pointcut and the empty set
> >
> > AspectJ has a mechanism for specifying that a pointcut matches nothing. 
> >  You specify no body at all, i.e.
> >    pointcut pc();
> >
> > There have been complaints that this is confusing to people because it 
> > looks too much like an abstract pointcut declaration.  For 1.2, we will 
> > consider providing a guarantee that if(false) will always be optimized 
> > away as matching nothing; however, I'm always concerned about having two 
> > roughly equivalent ways of saying the same thing in a programming language.
> >
> > -Jim
> >
> >
> > Dean Wampler wrote:
> >
> > > I don't understand the internals of ajc, but the error messages also 
> > > indicate to me that "if (false)" still results in some sort of 
> > > evaluation at all join points and hence it still imposes a lot of 
> > > overhead during the build. True? If so, a way to really turn it off 
> > > "completely" would be nice (or some sort of alternative mechanism  ....)
> > >
> > > dean
> > >
> > > Macneil Shonle wrote:
> > >
> > >
> > > > Hi all,
> > > >
> > > > This is a minor feature request, but something I'd like to see. Sometimes
> > > > I want to disable a pointcut in my development (essentially commenting it
> > > > out). I used to do this by making the pointcut be "if (false)" but this
> > > > creates errors for after advice when expection handlers are present:
> > > >
> > > > <...>
> > > > Thanks,
> > > > Macneil
> >
> >
> >
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