+ (format #t "Removes first entity:~%~a~%~a~%~%" entities components)
+
+ (receive (e c k) (new-entity (list (make-a 1 2) (make-b)) entities components)
+ (set! entities e)
+ (set! components c)
+ (set! key k)
+ (display k) (newline))
+ (format #t "New entity with a and b:~%~a~%~a~%~%" entities components)
+
+ (receive (e c) (set-entities `((,key . ((b . #f) ,(make-a 50 50))) (#f . (,(make-a 1000 1000)))) entities components)
+ (set! entities e)
+ (set! components c))
+ (format #t "Last entity removes b and changes a, and new entity with a:~%~a~%~a~%~%" entities components)
+
+ (receive (e c) (set-entities `((,key . #f)) entities components)
+ (set! entities e)
+ (set! components c))
+ (format #t "Remove last entity:~%~a~%~a~%~%" entities components)