> That's how it's supposed to be. Especially scheme tries to be nothing else 
> but just the minimal "functional assembly language". So one can put other 
> languages on top of it.

the words "functional" and "minimal" may be considered contradictory as the basic
primitive of functional programming, beta reduction, is a very heavy operation that
can successfully be decomposed into more lightweight operations like:

    - state change + conditional branching.
    - continuation passing
    - name-passing interaction.

(of those the third is the most elementary and general and encompasses the others).
putting any of those on top of beta-reduction generally leads to something ugly.
functional abstractions are extremely useful in many computational situations, but
they are high-level, not something one can use successfully as a foundation to start
from. several decades of failed attempts at founding (the semantics of) computation
on lambda calculus shows this. the difficulties of finding convincing hoare-logics for
ML-like languages, a problem that has really only been solved this year, and on the
basis of pi-calculus, is another indication in this direction.

as an aside, are there any good program logics for languages with macro-facilities like
lisp-dialects?

martin