From de5880169b1eb14a7e2dd57f42916e61f53832ba Mon Sep 17 00:00:00 2001
From: Matthew Wang <matt@matthewwang.me>
Date: Mon, 23 Oct 2023 01:14:01 -0700
Subject: [PATCH] Add check to see if scratch is valid/fix bug

---
 src/builder/bdd/robdd.rs | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/builder/bdd/robdd.rs b/src/builder/bdd/robdd.rs
index a95ec6fd..ea4e6255 100644
--- a/src/builder/bdd/robdd.rs
+++ b/src/builder/bdd/robdd.rs
@@ -190,10 +190,12 @@ impl<'a, T: IteTable<'a, BddPtr<'a>> + Default> RobddBuilder<'a, T> {
                 match bdd.scratch::<usize>() {
                     None => (),
                     Some(v) => {
-                        return if bdd.is_neg() {
-                            alloc[v].neg()
-                        } else {
-                            alloc[v]
+                        if alloc.len() > v {
+                            return if bdd.is_neg() {
+                                alloc[v].neg()
+                            } else {
+                                alloc[v]
+                            };
                         }
                     }
                 };