References: MACRO-FUNCTION, p. 144
MACROLET, pp. 113-4
&ENVIRONMENT, pp. 145-6
MACROEXPAND and MACROEXPAND-1, pp. 151-2
Edit history: Version 1, Pavel, March 21, 1988
Version 2, Masinter, 8-Jun-88, (as per cleanup discussion)
The &ENVIRONMENT argument to a macro-expansion function may only be used as
second argument to the functions MACROEXPAND and MACROEXPAND-1. It is
more convenient, however, to be able to work directly with the more
function MACRO-FUNCTION, on which MACROEXPAND and MACROEXPAND-1 are
based. However, since MACRO-FUNCTION does not take an environment
cannot be used in situations in which that environment must be taken into
Add an optional second argument to MACRO-FUNCTION, that argument being an
environment that was passed as the &ENVIRONMENT argument to some macro
function. If the argument is not given, or the argument is NIL, the null
environment is used. MACRO-FUNCTION will now consider macro definitions
that environment in preference to ones in the global environment. It is an
to supply the environment argument in a use of MACRO-FUNCTION as a SETF
(macrolet ((foo (&environment env)
(if (macro-function 'bar env)
(macrolet ((bar () :beep))
=> (no yes)
(setf (macro-function 'bar env) ...) is an error.
Intuitively, the more primitive operation in macro expansion is
not MACROEXPAND or MACROEXPAND-1, yet the environment argument can only be
supplied to the latter functions and not to the former one. By changing
state of affairs, the model of macro expansion becomes somewhat simpler.
more flexible use of the facility is enabled.
Xerox Common Lisp already implements this proposal. Symbolics Common Lisp,
and Kyoto Common Lisp do not. Lucid Common Lisp did not, but version 3.0
Cost to Implementors:
This is presumably a simple change to make, a small matter of moving the
environment-searching code from MACROEXPAND-1 to MACRO-FUNCTION.
Cost to Users:
The change is upward-compatible and so poses no cost to users.
Cost of non-adoption:
One more (small) semantic wart on the language.
The function that users think of as being more primitive really is.
This slightly cleans up the language.
This issue was discussed starting in January 1987, but got tangled in
a web of other related proposals. In its current form, the only objections
have been that some other proposal or committee might otherwise change
macro handling, or that this proposal doesn't fix enough of the problems.