+(define-syntax make-system
+ (syntax-rules ()
+ ((_ component-types system-func)
+ (lambda (entities components)
+ (let* ((e (find-entities-by-components components 'component-types))
+ (e* (map (lambda (x) (assoc x entities)) e))
+ (e** (map (lambda (x) (cons (car x) (filter (lambda (x) (memq (car x) 'component-types)) (cdr x)))) e*))
+ (res (system-func e**)))
+ (lambda* (#:optional (entities2 #f) (components2 #f))
+ (let ((e (if (and entities2 components2) entities2 entities))
+ (c (if (and entities2 components2) components2 components)))
+ (modify-entities res e c))))))))
+
+(define-syntax define-system
+ (syntax-rules ()
+ ((_ (name . component-types) system-func)
+ (define name (make-system component-types system-func)))))