+;;; @@ Lisp language features.
+
+(defmacro-maybe push (newelt listname)
+ "Add NEWELT to the list stored in the symbol LISTNAME.
+This is equivalent to (setq LISTNAME (cons NEWELT LISTNAME)).
+LISTNAME must be a symbol."
+ (list 'setq listname
+ (list 'cons newelt listname)))
+
+(defmacro-maybe pop (listname)
+ "Return the first element of LISTNAME's value, and remove it from the list.
+LISTNAME must be a symbol whose value is a list.
+If the value is nil, `pop' returns nil but does not actually
+change the list."
+ (list 'prog1 (list 'car listname)
+ (list 'setq listname (list 'cdr listname))))
+
+(defmacro-maybe when (cond &rest body)
+ "If COND yields non-nil, do BODY, else return nil."
+ (list 'if cond (cons 'progn body)))
+;; (def-edebug-spec when (&rest form))
+
+(defmacro-maybe unless (cond &rest body)
+ "If COND yields nil, do BODY, else return nil."
+ (cons 'if (cons cond (cons nil body))))
+;; (def-edebug-spec unless (&rest form))
+
+(defsubst-maybe caar (x)
+ "Return the car of the car of X."
+ (car (car x)))
+
+(defsubst-maybe cadr (x)
+ "Return the car of the cdr of X."
+ (car (cdr x)))
+
+(defsubst-maybe cdar (x)
+ "Return the cdr of the car of X."
+ (cdr (car x)))
+
+(defsubst-maybe cddr (x)
+ "Return the cdr of the cdr of X."
+ (cdr (cdr x)))
+
+(defun-maybe last (x &optional n)
+ "Return the last link of the list X. Its car is the last element.
+If X is nil, return nil.
+If N is non-nil, return the Nth-to-last link of X.
+If N is bigger than the length of X, return X."
+ (if n
+ (let ((m 0) (p x))
+ (while (consp p)
+ (setq m (1+ m) p (cdr p)))
+ (if (<= n 0) p
+ (if (< n m) (nthcdr (- m n) x) x)))
+ (while (cdr x)
+ (setq x (cdr x)))
+ x))
+
+;; Actually, `butlast' and `nbutlast' are defined in lisp/cl.el.
+(defun-maybe butlast (x &optional n)
+ "Returns a copy of LIST with the last N elements removed."
+ (if (and n (<= n 0)) x
+ (nbutlast (copy-sequence x) n)))
+
+(defun-maybe nbutlast (x &optional n)
+ "Modifies LIST to remove the last N elements."
+ (let ((m (length x)))
+ (or n (setq n 1))
+ (and (< n m)
+ (progn
+ (if (> n 0) (setcdr (nthcdr (- (1- m) n) x) nil))
+ x))))
+
+;; Emacs 20.3 and later: (assoc-default KEY ALIST &optional TEST DEFAULT)
+(defun-maybe assoc-default (key alist &optional test default)
+ "Find object KEY in a pseudo-alist ALIST.
+ALIST is a list of conses or objects. Each element (or the element's car,
+if it is a cons) is compared with KEY by evaluating (TEST (car elt) KEY).
+If that is non-nil, the element matches;
+then `assoc-default' returns the element's cdr, if it is a cons,
+or DEFAULT if the element is not a cons.
+
+If no element matches, the value is nil.
+If TEST is omitted or nil, `equal' is used."
+ (let (found (tail alist) value)
+ (while (and tail (not found))
+ (let ((elt (car tail)))
+ (when (funcall (or test 'equal) (if (consp elt) (car elt) elt) key)
+ (setq found t value (if (consp elt) (cdr elt) default))))
+ (setq tail (cdr tail)))
+ value))
+
+;; The following two function use `compare-strings', which we don't
+;; support yet.
+;; (defun assoc-ignore-case (key alist))
+;; (defun assoc-ignore-representation (key alist))
+
+;; Emacs 19.29/XEmacs 19.14(?) and later: (rassoc KEY LIST)
+;; Actually, `rassoc' is defined in src/fns.c.
+(defun-maybe rassoc (key list)
+ "Return non-nil if KEY is `equal' to the cdr of an element of LIST.
+The value is actually the element of LIST whose cdr equals KEY.
+Elements of LIST that are not conses are ignored."
+ (catch 'found
+ (while list
+ (cond ((not (consp (car list))))
+ ((equal (cdr (car list)) key)
+ (throw 'found (car list))))
+ (setq list (cdr list)))))
+
+;;; Define `functionp' here because "localhook" uses it.
+
+;; Emacs 20.1/XEmacs 20.3 (but first appeared in Epoch?): (functionp OBJECT)
+(defun-maybe functionp (object)
+ "Non-nil if OBJECT is a type of object that can be called as a function."
+ (or (subrp object) (byte-code-function-p object)
+ (eq (car-safe object) 'lambda)
+ (and (symbolp object) (fboundp object))))
+
+;;; @@ Hook manipulation functions.
+
+;; "localhook" package is written for Emacs 19.28 and earlier.
+;; `run-hooks' was a lisp function in Emacs 19.29 and earlier.
+;; So, in Emacs 19.29, `run-hooks' and others will be overrided.
+;; But, who cares it?
+(static-unless (subrp (symbol-function 'run-hooks))
+ (require 'localhook))
+
+;; Emacs 19.29/XEmacs 19.14(?) and later: (add-to-list LIST-VAR ELEMENT)