> This works ok except when it comes to use SimplifyingFilterVisitor
> down in the call chain (an hence any DuplicatingFilterVisitor
> specialization), because visit(Function) will try to return a new
> instance looking up the function factory by name, which does not
> exist.
>
>
Can you detect this case, and "reuse" the original function with warning?
> For this reason, and in order to keep it as simple as possible, I
> wonder if it would be ok to say that VolatileFunctions are not
> "cloneable", and so instruct DuplicatingFilterVisitor.visit(Function,
> Object) not to go through the SPI lookup for VolatileFunctions, but
> return them directly.
>
>
I have a hesitation there as that is not quite the meaning of VolatileFunction
we were going for; but I see how it can work.
I will note, that if you cannot make a copy, then any simplifications made on
the parameters to your function cannot be accepted.
> Another possibility is to add a separate marker interface, but I would
> rather avoid bloating the API.
>
>
See if you can detect the failure; and use a warning (avoids the API bloat
without introducing a marker interface).
1) Suggestion not just a marker interface but something that lets you duplicate:
interface class InternalFunction extends Function {
InternalFunction duplicate( Expression... params);
}
2) Special case DuplicatingFilterVisitor - i.e. check for the marker interface
"Clonable" and a public "clone" method you can call via reflection
Jody
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