On 2004-05-15, Andreas Fuchs <asf@boinkor.net> wrote:
;;; A few months ago, there was a thread about FUNCALL and APPLY on ;;; c.l.l. I wrote this code to show how APPLY might be defined in ;;; terms of FUNCALL.
;;; As some of you noted, this version is buggy: it doesn't do the ;;; list-as-last-arg magick correctly. Let's fix that: ;;; This code fixes that: (defun apply-definer (max-args) `(defun apply-1 (f args) (case (length args) ,@(loop for arg-count from 0 to max-args collect `((,arg-count) (funcall f ,@(loop for arg-idx from 0 to (1- arg-count) collect `(nth ,arg-idx args))))) (otherwise (error ,(format nil "Can't apply to more than ~A args" max-args)))))) (defmacro define-apply (max-args) (apply-definer (etypecase max-args (symbol (symbol-value max-args)) (number max-args)))) (defun my-apply (f &rest args) (let ((last-arg (first (last args)))) (apply-1 f (if (listp last-arg) (append (butlast args) last-arg) args)))) (define-apply ; call-arguments-limit ; might be a bit much for the poor impl 20 ; let's be humane ) ;;; example: #| CL-USER> (defun print-all (&rest args) (loop for arg in args do (print arg))) CL-USER> (my-apply #'print-all 1 2 3 '(1 2 3)) 1 2 3 1 2 3 NIL |#
;;; License: BSD-sans-advertising.
-- Andreas Fuchs, <asf@boinkor.net>, asf@jabber.at, antifuchs