From 84840ede6646ed793b61cdd889d3f57ab05e9311 Mon Sep 17 00:00:00 2001
From: Gene Pasquet <dev@etenil.net>
Date: Wed, 8 Apr 2026 01:32:55 +0100
Subject: Refactor to be functional

---
 demo/shmup.scm | 54 +++++++++++++++++++++++++++++-------------------------
 1 file changed, 29 insertions(+), 25 deletions(-)

(limited to 'demo/shmup.scm')

diff --git a/demo/shmup.scm b/demo/shmup.scm
index 97779a8..ab09957 100644
--- a/demo/shmup.scm
+++ b/demo/shmup.scm
@@ -61,6 +61,10 @@
   (let ((y (entity-ref e #:y 0)))
     (and (> y -20) (< y (+ +screen-height+ 20)))))
 
+(define (scene-remove-dead scene)
+  (let ((dead (find-dead (scene-entities scene))))
+    (scene-filter-entities scene (lambda (e) (not (memq e dead))))))
+
 ;; ── Update helpers ───────────────────────────────────────────────────────────
 
 (define (player-vx input)
@@ -72,26 +76,27 @@
   (entity-set player #:x
     (max 0 (min (- +screen-width+ 16) (entity-ref player #:x 0)))))
 
-(define (update-player player input scene)
+(define (update-player player input)
   (let ((updated (chain player
                         (entity-set _ #:vx (player-vx input))
                         (apply-velocity-x _)
                         (clamp-player-x _))))
     (when (input-pressed? input 'a)
-      (play-sound 'shoot)
-      (scene-add-entity scene
-        (make-bullet (+ (entity-ref updated #:x 0) 6) 340)))
-    updated))
+      (play-sound 'shoot))
+    (if (input-pressed? input 'a)
+        (values updated
+                (list (make-bullet (+ (entity-ref updated #:x 0) 6) 340)))
+        (values updated '()))))
 
 (define (move-projectile e)
   (chain e
          (entity-set _ #:x (+ (entity-ref e #:x 0) (entity-ref e #:vx 0)))
          (entity-set _ #:y (+ (entity-ref e #:y 0) (entity-ref e #:vy 0)))))
 
-(define (maybe-spawn-enemy! scene)
-  (when (zero? (modulo *frame-count* +spawn-interval+))
-    (scene-add-entity scene
-      (make-enemy (+ 20 (* (pseudo-random-integer 28) 20))))))
+(define (maybe-spawn-enemies)
+  (if (zero? (modulo *frame-count* +spawn-interval+))
+      (list (make-enemy (+ 20 (* (pseudo-random-integer 28) 20))))
+      '()))
 
 ;; ── Render ───────────────────────────────────────────────────────────────────
 
@@ -132,22 +137,21 @@
 
     update: (lambda (game dt)
       (set! *frame-count* (+ *frame-count* 1))
-      (let* ((input  (game-input game))
-             (scene  (game-scene game))
-             (player (car (scene-entities scene)))
-             (player (update-player player input scene)))
-        (maybe-spawn-enemy! scene)
-        ;; Replace player, then move all projectiles
-        (scene-entities-set! scene
-          (cons player (filter (lambda (e) (not (eq? (entity-type e) 'player)))
-                               (scene-entities scene))))
-        (scene-update-entities scene
-          (lambda (e) (if (eq? (entity-type e) 'player) e (move-projectile e))))
-        ;; Remove bullet/enemy collisions, then out-of-bounds
-        (let ((dead (find-dead (scene-entities scene))))
-          (scene-filter-entities scene (lambda (e) (not (memq e dead)))))
-        (scene-filter-entities scene
-          (lambda (e) (or (eq? (entity-type e) 'player) (in-bounds? e))))))
+      (let* ((input   (game-input game))
+             (scene   (game-scene game))
+             (player  (car (scene-entities scene))))
+        (receive (player new-entities) (update-player player input)
+          (let* ((others  (filter (lambda (e) (not (eq? (entity-type e) 'player)))
+                                  (scene-entities scene)))
+                 (spawned (maybe-spawn-enemies))
+                 (all     (cons player (append new-entities spawned others))))
+            (game-scene-set! game
+              (chain (update-scene scene entities: all)
+                (scene-update-entities _
+                  (lambda (e) (if (eq? (entity-type e) 'player) e (move-projectile e))))
+                (scene-remove-dead _)
+                (scene-filter-entities _
+                  (lambda (e) (or (eq? (entity-type e) 'player) (in-bounds? e))))))))))
 
     render: (lambda (game)
       (for-each (cut draw-shmup-entity (game-renderer game) <>)
-- 
cgit v1.2.3