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(add-hook): Change a single function into a list.

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Richard M. Stallman 1993-08-02 07:23:07 +00:00
parent 47f3858d11
commit 322959764a
1 changed files with 20 additions and 6 deletions
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26
lisp/subr.el
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@ -296,7 +296,8 @@ The normal global definition of the character C-x indirects to this keymap.")
(defun event-modifiers (event)
"Returns a list of symbols representing the modifier keys in event EVENT.
The elements of the list may include `meta', `control',
`shift', `hyper', `super', `alt', `click', `drag', and `down'."
`shift', `hyper', `super', `alt', `click', `double', `triple', `drag',
and `down'."
(let ((type event))
(if (listp type)
(setq type (car type)))
@ -352,6 +353,11 @@ The return value is of the form
The `posn-' functions access elements of such lists."
(nth (if (consp (nth 2 event)) 2 1) event))
(defsubst event-click-count (event)
"Return the multi-click count of EVENT, a click or drag event.
The return value is a positive integer."
(if (integerp (nth 2 event)) (nth 2 event) 1))
(defsubst posn-window (position)
"Return the window in POSITION.
POSITION should be a list of the form
@ -460,12 +466,20 @@ If it is a list, the elements are called, in order, with no arguments."
Don't change it.")
(defun add-hook (hook function &optional append)
"Add to the value of HOOK the function FUNCTION unless already present (it
becomes the first hook on the list unless optional APPEND is non-nil, in
which case it becomes the last). HOOK should be a symbol, and FUNCTION may be
any valid function. HOOK's value should be a list of functions, not a single
function. If HOOK is void, it is first set to nil."
"Add to the value of HOOK the function FUNCTION.
FUNCTION is not added if already present.
FUNCTION is added (if necessary) at the beginning of the hook list
unless the optional argument APPEND is non-nil, in which case
FUNCTION is added at the end.
HOOK should be a symbol, and FUNCTION may be any valid function. If
HOOK is void, it is first set to nil. If HOOK's value is a single
function, it is changed to a list of functions."
(or (boundp hook) (set hook nil))
;; If the hook value is a single function, turn it into a list.
(let ((old (symbol-value hook)))
(if (or (not (listp old)) (eq (car old) 'lambda))
(set hook (list old))))
(or (if (consp function)
;; Clever way to tell whether a given lambda-expression
;; is equal to anything in the hook.