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5.3.1 apply [Function]

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 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, Evaluation, APPLY Forms as Places