[Small-cl-src] m-v-b* and d-b* (auto-ignoring arguments called _)

[Andreas Fuchs]

;;; Hi,
;;; 
;;; I hope this code makes a few functions (like decode-universal-time)
;;; more useful. Each of these functions replaces variables with a
;;; symbol-name of _ with a (declare (ignore))d gensym.
;;; 
;;; I'm sure everybody has already written something similar.
;;; "Somebody should write a CLRFI for that" (-:

(require :iterate)
;; Yeah, sorry.. the solution using LOOP was ugly as hell.

(defun replace-binds (binds)
  (iterate (for bind in binds)
           (typecase bind
             (cons
              (multiple-value-bind (result* ignore*) (replace-binds bind)
                (collecting result* into result)
                (appending ignore* into ignore)))
             (t
              (if (string-equal bind '_)
                  (let ((sym (gensym)))
                    (collect sym into result)
                    (collect sym into ignore))
                  (collect bind into result))))
           (finally (return (values result ignore)))))

(defmacro destructuring-bind* (bind-list obj &rest body)
  (multiple-value-bind (binds ignores) (replace-binds bind-list)
    `(destructuring-bind ,binds ,obj
       (declare (ignore , at ignores))
       , at body)))

(defmacro multiple-value-bind* (bind-list obj &rest body)
  (multiple-value-bind (binds ignores) (replace-binds bind-list)
    `(multiple-value-bind ,binds ,obj
       (declare (ignore , at ignores))
       , at body)))

;;; Have fun,
-- 
Andreas Fuchs, <asf at boinkor.net>, asf at jabber.at, antifuchs