From 4ddcdfb6a9bf72818a422b752a0598705ecd2c43 Mon Sep 17 00:00:00 2001
From: Tony Garnock-Jones <tonygarnockjones@gmail.com>
Date: Sun, 21 Oct 2018 13:32:06 +0100
Subject: [PATCH] Present-to-absent check is necessary in assertion removal
 handler

---
 syndicate/HOWITWORKS.md | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/syndicate/HOWITWORKS.md b/syndicate/HOWITWORKS.md
index 898df22..7ad4761 100644
--- a/syndicate/HOWITWORKS.md
+++ b/syndicate/HOWITWORKS.md
@@ -444,8 +444,9 @@ check followed by zero or more (move, check) pairs.
         del_leaf (leafcache, _) v = leafcache -= v
         del_handler (bag, f_table) vs =
           bag[vs] -= 1
-          for f in f_table
-              f "-" vs
+          if vs not in bag then
+              for f in f_table
+                  f "-" vs
 
 **Definition.** The procedures `addAssertion` and `removeAssertion`
   install and remove an assertion `v` into the given index,