ANSI Common Lisp 3 Evaluation and Compilation 3.8 Dictionary Evaluation and Compilation
symbol &optional environment
(macro-function symbol &optional environment) new-function)
- Arguments and Values:
symbol - a symbol.
environment - an environment object.
function - a macro function or nil.
new-function - a macro function.
Determines whether symbol has a function definition
as a macro in the specified environment.
If so, the macro expansion function, a function of two arguments,
is returned. If symbol has no function definition
in the lexical environment environment, or its definition
is not a macro, macro-function returns nil.
It is possible for both macro-function and
to return true of symbol. The macro definition must
be available for use by programs that understand only the standard
Common Lisp special forms.
(defmacro macfun (x) '(macro-function 'macfun)) MACFUN
(not (macro-function 'macfun)) false
(macrolet ((foo (&environment env)
(if (macro-function 'bar env)
(macrolet ((bar () :beep))
- Affected By:
(setf macro-function), defmacro, and macrolet.
- Exceptional Situations:
The consequences are undefined if environment is non-nil
in a use of setf of macro-function.
- See Also:
defmacro, Section 3.1 Evaluation
setf can be used with macro-function to install
a macro as a symbol's global function definition:
(setf (macro-function symbol) fn)
The value installed must be a function that accepts two arguments,
the entire macro call and an environment,
and computes the expansion for that call.
Performing this operation causes symbol to have only that
macro definition as its global function definition; any previous
definition, whether as a macro or as a
function, is lost.
- Allegro CL Implementation Details: