From: Javier Sancho <jsf@jsancho.org>
Date: Tue, 14 Jan 2014 17:58:39 +0000 (+0100)
Subject: New way for returning results from systems
X-Git-Url: https://git.jsancho.org/?p=gacela.git;a=commitdiff_plain;h=405b60cfd27f00e8dda02e19abe09bf7990bfbc2

New way for returning results from systems

* src/system: New type entities-changes that encapsulates entities
              modifications. A system that only does I/O operations
              doesn't must to return an entities-changes object.

* src/examples/composing-systems.scm: Updated example

* src/examples/making-systems.scm: Updated example
---

diff --git a/src/examples/composing-systems.scm b/src/examples/composing-systems.scm
index 7742b81..ef6e1e0 100644
--- a/src/examples/composing-systems.scm
+++ b/src/examples/composing-systems.scm
@@ -22,17 +22,17 @@
 
 (define-system s1 ((with-l (l)))
   (sleep 3)
-  (map
-   (lambda (e)
-     (set-entity-components (get-key e) `(l . ,(cons 1 (get-component 'l e)))))
-   with-l))
+  (entities-changes
+   (map (lambda (e)
+	  (set-entity-components (get-key e) `(l . ,(cons 1 (get-component 'l e)))))
+	with-l)))
 
 (define-system s2 ((with-l (l)))
   (sleep 4)
-  (map
-   (lambda (e)
-     (set-entity-components (get-key e) `(l . ,(cons 2 (get-component 'l e)))))
-   with-l))
+  (entities-changes
+   (map (lambda (e)
+	  (set-entity-components (get-key e) `(l . ,(cons 2 (get-component 'l e)))))
+	with-l)))
 
 (define (composing-with-join)
   (let ((entities '())
diff --git a/src/examples/making-systems.scm b/src/examples/making-systems.scm
index c049a90..545b7e7 100644
--- a/src/examples/making-systems.scm
+++ b/src/examples/making-systems.scm
@@ -23,15 +23,15 @@
 (define-component a x y)
 
 (define-system s1 ()
-  (list (new-entity (make-a 1 2))
-	(new-entity (make-a 10 20))))
+  (entities-changes
+   (list (new-entity (make-a 1 2))
+	 (new-entity (make-a 10 20)))))
 
 (define-system s2 ((with-a (a)))
   (for-each
    (lambda (e)
      (format #t "Key: ~a  Component: ~a~%" (get-key e) (get-component 'a e)))
-   with-a)
-  '())
+   with-a))
   
 (define (making-systems)
   (let ((entities '())
diff --git a/src/system.scm b/src/system.scm
index 9654cff..5a70cb5 100644
--- a/src/system.scm
+++ b/src/system.scm
@@ -187,6 +187,11 @@
 
 ;;; Making systems
 
+(define-record-type entities-changes-type
+  (entities-changes changes)
+  entities-changes?
+  (changes get-entities-changes))
+
 (define* (find-entities-by-components c t)
   (cond ((null? t) '())
 	(else
@@ -213,7 +218,7 @@
 	   (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)))))))))
+	       (modify-entities (if (entities-changes? res) (get-entities-changes res) '()) e c)))))))))
 
 (define-syntax define-system
   (syntax-rules ()
@@ -274,7 +279,10 @@
 	(else
 	 (apply join-systems systems))))
 
-(export find-entities-by-components
+(export entities-changes
+	entities-changes?
+	get-entities-changes
+	find-entities-by-components
 	define-system
 	make-system
 	join-systems