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Delete Item from a null-terminated list linked by the accessor function Next
that is stored in Place. Item must appear exactly once in the list."
(multiple-value-bind
(temps vals stores store access)
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(let ((n-item (gensym))
(n-place (gensym))
(n-current (gensym))
(n-prev (gensym)))
`(let* (,@(mapcar #'list temps vals)
(,n-place ,access)
(,n-item ,item))
(if (eq ,n-place ,n-item)
(let ((,(first stores) (,next ,n-place)))
,store)
(do ((,n-prev ,n-place ,n-current)
(,n-current (,next ,n-place)
(,next ,n-current)))
((eq ,n-current ,n-item)
(setf (,next ,n-prev)
(,next ,n-current)))))
(undefined-value)))))
;;; Push-In -- Interface
;;;
(defmacro push-in (next item place &environment env)
"Push Item onto a list linked by the accessor function Next that is stored in
Place."
(multiple-value-bind
(temps vals stores store access)
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`(let (,@(mapcar #'list temps vals)
(,(first stores) ,item))
(setf (,next ,(first stores)) ,access)
,store
(undefined-value))))
;;; Compiler-Constantp -- Interface
;;;
;;; We don't want to assume that a variable is a constant just because it is
;;; in the current lisp environment.
;;;
;;; ### For now, just use CONSTANTP to avoid bootstrapping problems with having
;;; to have the INFO database available at meta-compile time.
;;;
(proclaim '(function compiler-constantp (t) boolean))
(defun compiler-constantp (exp)
"Like constantp, only uses the compilation environment rather than the
current Lisp environment."
#|
(if (symbolp exp)
(eq (info variable kind exp) :constant)
(constantp exp))
|#
(constantp exp))