history list symbol. The variable @code{history-delete-duplicates}
specifies whether to delete duplicates in history.
+@defun add-to-history history-var newelt &optional maxelt keep-dups
+This function adds a new element @var{newelt} to the history list
+stored in the variable @var{history-var}, and returns the updated
+history list. By default, the list length is limited by the value
+specified by @code{history-length} (described below), but the optional
+argument @var{maxelt} overrides that. The possible values of
+@var{maxelt} have the same meaning as the values of
+@code{history-length}.
+
+Duplicate members are removed from the history list, unless
+@code{history-delete-duplicates} is @code{nil} or the second optional
+argument of this function @var{keep-dups} is non-@code{nil}.
+@end defun
+
@defvar history-length
The value of this variable specifies the maximum length for all
history lists that don't specify their own maximum lengths. If the
value is @code{t}, that means there no maximum (don't delete old
-elements).
+elements). The value of @code{history-length} property of the history
+list variable's symbol, if set, overrides this variable for that
+particular history list.
@end defvar
@defvar history-delete-duplicates