R-ObjC branch
---------------

This is a branch of R where all R objects are at the same time
Objective-C objects. This means that any R object can respond to ObjC
messages.

The reason for this branch is to experiment with new features, types
and approaches in R. The use of the Objective-C architecture allows
us to plug-in different evaluators for different objects, change the
semantics, memory model etc. easily.

This branch is not targetted at real-life use, instead it is a part of
the Aleph project to develop and test new ideas for statistical
computing. (Basically the overhead buys flecibility but not speed).

* What is the major difference?

All SEXPs in this branch have an additional pointer (before the
regular SEXP header) which points to the ObjC class (Class isa). This
allows ObjC dispatch in addition to the regular R facilities.

- public class definitions are in include/RObjC.h
- implementations are currently in src/main/objc.m but that is
  likely to change (into separate .m files)

* Why Objective-C?

Objective-C is dynamic, has introspection/reflection, has very little
overhead and the way objects are implemented allows a very
non-intrusive adaptation of existing objects into ObjC objects.

* Next goals

- add hooks in the evaluator and primitives to dispatch to ObjC when
  necessary


Simon Urbanek 10/2007