5.3.39 constantly [Function]

constantly value ⇒ function

Arguments and Values::

value—an object.

function—a function.

Description::

constantly returns a function that accepts any number of arguments, that has no side-effects, and that always returns value.

Examples::

 (mapcar (constantly 3) '(a b c d)) ⇒  (3 3 3 3)
 (defmacro with-vars (vars &body forms)
   `((lambda ,vars ,@forms) ,@(mapcar (constantly nil) vars)))
⇒  WITH-VARS
 (macroexpand '(with-vars (a b) (setq a 3 b (* a a)) (list a b)))
⇒  ((LAMBDA (A B) (SETQ A 3 B (* A A)) (LIST A B)) NIL NIL), true

See Also::

not

Notes::

constantly could be defined by:

 (defun constantly (object)
   #'(lambda (&rest arguments) object))