macros expanding into definitions

["Mark Friedman" <markf@martigny.ai.mit.edu>]

** ... I would still prefer that (if a variable is DEFINEd) a DEFINE
** of a variable be required to precede SET!s of that variable.  This
** is currently required both at top level and internally.  I think
** most beginners are used to defining variables before use; so this
** would eliminate one source of confusion about scope as illustrated
** above.

I'm still not sure that I want to screw around with internal defines,
but if we must, I might actually like to see internal defines start a
new scope and have previous assignments refer to outer scopes. Doesn't
ML have something like this (at least at top-level).

-Mark