From 354fad2b1d8a626b0df6f83d44f0b0317876febe Mon Sep 17 00:00:00 2001
From: Sergiu Ivanov <sivanov@colimite.fr>
Date: Sun, 22 Nov 2020 22:50:29 +0100
Subject: [PATCH] network: Roll back update to its previous version.

I thought I was clever to rewrite update using for/hash, but in fact
this new version only included the updated variables in the new
state :D
---
 networks.rkt | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/networks.rkt b/networks.rkt
index 2923a53..426a91a 100644
--- a/networks.rkt
+++ b/networks.rkt
@@ -203,8 +203,10 @@
 ;;; Given a state s updates all the variables from xs.
 (define (update network s xs)
   (define funcs (network-functions network))
-  (for/hash ([x xs])
-    (values x ((hash-ref funcs x) s))))
+  (for/fold ([new-s s])
+            ([x xs])
+    (define fx (hash-ref funcs x))
+    (hash-set new-s x (fx s))))
 
 (module+ test
   (test-case "basic definitions"