apply
apply Function
Syntax:
apply function &rest args+ → {result}*
Arguments and Values:
function—a function designator .
args—a spreadable argument list designator .
results—the values returned by function.
Description:
Applies the function to the args.
When the function receives its arguments via &rest, it is permissible (but not required) for the implementation to bind the rest parameter to an object that shares structure with the last argument to apply. Because a function can neither detect whether it was called via apply nor whether (if so) the last argument to apply was a constant, conforming programs must neither rely on the list structure of a rest list to be freshly consed, nor modify that list structure.
setf can be used with apply in certain circumstances; see Section 5.1.2.5 (APPLY Forms as Places).
Examples:
(setq f ’+) → +
(apply f ’(1 2)) → 3
(setq f #’-) → #<FUNCTION ->
(apply f ’(1 2)) → -1
(apply #’max 3 5 ’(2 7 3)) → 7
(apply ’cons ’((+ 2 3) 4)) → ((+ 2 3) . 4)
(apply #’+ ’()) → 0
(defparameter \*some-list\* ’(a b c))
(defun strange-test (&rest x) (eq x \*some-list\*))
(apply #’strange-test \*some-list\*) → implementation-dependent
(defun bad-boy (&rest x) (rplacd x ’y))
(bad-boy ’a ’b ’c) has undefined consequences.
(apply #’bad-boy \*some-list\*) has undefined consequences.
(defun foo (size &rest keys &key double &allow-other-keys)
(let ((v (apply #’make-array size :allow-other-keys t keys)))
(if double (concatenate (type-of v) v v) v)))
(foo 4 :initial-contents ’(a b c d) :double t)
→ #(A B C D A B C D)
See Also:
funcall, fdefinition, function, Section 3.1 (Evaluation), Section 5.1.2.5 (APPLY Forms as Places)
Expanded Reference: apply
TODO: Please contribute to this page by adding explanations and examples
(apply )