constantly

constantly Function

Syntax:

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:

identity

Notes:

constantly could be defined by:

(defun constantly (object)

#’(lambda (&rest arguments) object))

every, some, notevery, notany

Expanded Reference: constantly

tip

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