From 6fe031e678d66c648367726cd50613d5a861bd84 Mon Sep 17 00:00:00 2001
From: Tony Garnock-Jones <tonyg@leastfixedpoint.com>
Date: Fri, 18 Jun 2021 22:19:54 +0200
Subject: [PATCH] once

---
 syndicate/syntax.rkt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/syndicate/syntax.rkt b/syndicate/syntax.rkt
index 257ce91..d328064 100644
--- a/syndicate/syntax.rkt
+++ b/syndicate/syntax.rkt
@@ -34,6 +34,7 @@
          this-target
          at
          assert
+         once
          stop-on
          on
          during
@@ -320,6 +321,9 @@
                                                      (->preserve expr)
                                                      (void)))))))])))
 
+(define-syntax-rule (once [event expr ...] ...)
+  (react (stop-on event expr ...) ...))
+
 (define-syntax-rule (stop-on event expr ...)
   (on event (stop-current-facet expr ...)))