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Issue: FUNCTION-TYPE (version 10)
- To: CL-CLEANUP@sail.stanford.edu
- Subject: Issue: FUNCTION-TYPE (version 10)
- From: Jon L White <email@example.com>
- Date: Sat, 21 May 88 02:02:10 PDT
re: 5a. The value returned by SYMBOL-FUNCTION when FBOUNDP returns true
but the symbol denotes a macro or special form is not well-defined,
but SYMBOL-FUNCTION will not signal an error.
5b. Assuming that symbol is fbound[sic],
(FUNCTIONP (SYMBOL-FUNCTION symbol))
(AND (NOT (MACRO-FUNCTION symbol))
(NOT (SPECIAL-FORM-P symbol))).
I don't understand the motivation behind this point (5b). Since (5a) says
that SYMBOL-FUNCTION is permitted to return "something", and is not
"well-defined" in the case when the symbol names a macro or special form,
then what is the advantage of preventing it from returning a function?
I've seen lots of CL code like:
(defun foo-expander (x) `(QUOTE ,x))
(setf (macro-function 'FOO) #'foo-expander)
How will one fetch the current "expander function" for this macro?
Is the issue merely that some implementations will have to cons in order to
return a value for MACRO-FUNCTION? In that case, maybe we need a predicate
MACRO-P, just as there is a predicate SPECIAL-FORM-P.
-- JonL --