[Functor] [patch] IsInstanceOf

[Arnd Kohrs <ak...@free.fr>]

Dear All,

I have started using the sandbox functors for my projects.  It seems 
that parts of the code may still need some streamlining.

I gave a shot at "IsInstanceOf".

Please receive attached a patch which changes IsInstanceOf from a 
UnaryPredicate to a BinaryPredicate (as the binary operator "instanceof" )

I tried to structure it in the same way as the Predicate "IsElementOf". 
In this way the code becomes more compact and more coherent in addition 
of providing all three kinds of Predicates.

Unfortunately, the changes are not backward compatible since it has 
become now a BinaryPredicate, which I hope it not of show-stopper 
importance at this stage of project.

Can the maintainers please consider the application of this patch.

I plan to regularly contribute to this projects in the future and I 
really hope that this project is not doomed, which the lack of exchange 
on its behalf may suggest.

Cheers,
Arnd.