Function constantly

Syntax:

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

Affected By:

None.

Exceptional Situations:

None.

See Also:

"not" => "identity" per Boyer/Kaufmann/Moore #10 (by X3J13 vote at May 4-5, 1994 meeting) -kmp 9-May-94identity

Notes:

constantly could be defined by:

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