(< oa ob)
oa)))))))
-(defun add-to-history (history-var newelt &optional maxelt)
+(defun add-to-history (history-var newelt &optional maxelt keep-all)
"Add NEWELT to the history list stored in the variable HISTORY-VAR.
Return the new history list.
If MAXELT is non-nil, it specifies the maximum length of the history.
Otherwise, the maximum history length is the value of the `history-length'
property on symbol HISTORY-VAR, if set, or the value of the `history-length'
variable.
-Remove duplicates of NEWELT unless `history-delete-duplicates' is nil."
+Remove duplicates of NEWELT if `history-delete-duplicates' is non-nil.
+If optional fourth arg KEEP-ALL is non-nil, add NEWELT to history even
+if it is empty or a duplicate."
(unless maxelt
(setq maxelt (or (get history-var 'history-length)
history-length)))
(let ((history (symbol-value history-var))
tail)
- (if history-delete-duplicates
- (setq history (delete newelt history)))
- (setq history (cons newelt history))
- (when (integerp maxelt)
- (if (= 0 maxelt)
- (setq history nil)
- (setq tail (nthcdr (1- maxelt) history))
- (when (consp tail)
- (setcdr tail nil))))
+ (when (and (listp history)
+ (or keep-all
+ (not (stringp newelt))
+ (> (length newelt) 0))
+ (or keep-all
+ (not (equal (car history) newelt))))
+ (if history-delete-duplicates
+ (delete newelt history))
+ (setq history (cons newelt history))
+ (when (integerp maxelt)
+ (if (= 0 maxelt)
+ (setq history nil)
+ (setq tail (nthcdr (1- maxelt) history))
+ (when (consp tail)
+ (setcdr tail nil)))))
(set history-var history)))
\f