I have implemented a small fexpr interpreter in Common Lisp based on Kernel http://web.cs.wpi.edu/~jshutt/kernel.html. Right now it's a Lisp 1, but I am considering trying to make it a more idiomatic extension of Common Lisp by making it a Lisp 2.
Part of the Lisp 2-ness of the Common Lisp evaluator is that the car of a form must name a function, macro, or special form. This name is either a symbol bound in the function name space, or a lambda expression. However, Kernel just requires the car evaluate to a combiner (this is what Kernel calls a generic operator). Obviously, in a Lisp 2, a symbol would evaluate to the value bound to it in the function name space. However, consider the following:
((returns-a-function) arg arg ...)
Would it be reasonable to allow this as a legal form as well?
I'm not arguing Common Lisp should work this way, but I seems to make sense in the context of a Kernel like evaluator.
Matt