[add] drop-unit-if

1 files changed, 7 insertions, 4 deletions

diff --git a/src/wheelwork.lisp b/src/wheelwork.lisp
index da432ba..b4c5431 100644
--- a/src/wheelwork.lisp
+++ b/src/wheelwork.lisp
@@ -9,17 +9,20 @@
 
 (defmethod add-unit ((unit unit))
   "Adds a unit to the display."
-  (assert *application*)
   (vector-push-extend unit (application-scene *application*) (1+ (length (application-scene *application*))))
   (setf (unit-in-scene-p unit) t))
 
 (defgeneric drop-unit (unit))
 (defmethod drop-unit ((unit unit))
   "A removes a unit from the display."
-  (assert *application*)
+  (setf (unit-in-scene-p unit) nil)
   (setf (application-scene *application*)
-        (delete unit (application-scene *application*)))
-  (setf (unit-in-scene-p unit) nil))
+        (delete unit (application-scene *application*))))
+
+(defun drop-unit-if (predicate)
+  "Removes all units from scene that satisfy the predicate."
+  (setf (application-scene *application*)
+        (delete-if predicate (application-scene *application*))))
 
 (defun start (app &key (x :centered) (y :centered))
   (sdl2:with-init (:everything)