[example] altered to use drop-unit-if

1 files changed, 2 insertions, 11 deletions

diff --git a/examples/09-ghoulspree.lisp b/examples/09-ghoulspree.lisp
index 896f470..33a5423 100644
--- a/examples/09-ghoulspree.lisp
+++ b/examples/09-ghoulspree.lisp
@@ -100,17 +100,8 @@ on which boundary VAL is outside of."
         (loop for ghoul across (ww::application-scene app)
               do (advance-pos ghoul)
               when gravity
-                do (apply-gravity-to ghoul accelleration)
-              when (out-of-bounds-p ghoul)
-                ;; note, it is generally a BadIdea™ to delete
-                ;; something from an array that you are iterating
-                ;; over. It only works as expected here b/c of
-                ;; implicit knowledge about the imlementation of the
-                ;; scene container. A safer way in most cases would be
-                ;; to `collect ghoul into drop-list` and then deleted
-                ;; all the collected ghouls in a `finally` clause,
-                ;; or to use ww::drop-unit-if in a `finally` clause.
-                do (ww:drop-unit ghoul))))) 
+                do (apply-gravity-to ghoul accelleration)))
+      (ww::drop-unit-if #'out-of-bounds-p))) 
 
 (defun random-sign ()
   (if (zerop (random 2)) -1 1))