From a606c62cbe83f7e8cc945c3b3c864f403af9204f Mon Sep 17 00:00:00 2001
From: Keith Alcock <github@keithalcock.com>
Date: Thu, 7 Jul 2022 11:36:08 -0700
Subject: [PATCH] Rewrite without null

---
 main/src/main/scala/org/clulab/dynet/Eisner.scala | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/main/src/main/scala/org/clulab/dynet/Eisner.scala b/main/src/main/scala/org/clulab/dynet/Eisner.scala
index af3740688..fbf48bf7d 100644
--- a/main/src/main/scala/org/clulab/dynet/Eisner.scala
+++ b/main/src/main/scala/org/clulab/dynet/Eisner.scala
@@ -245,7 +245,8 @@ class Eisner {
         val relativeHead = scores(i).maxBy(_._2)._1.toInt
         val depMod = i + 1
         val depHead = if (relativeHead == 0) 0 else depMod + relativeHead
-        val valid = dependencies(depMod).indices.contains(depHead) && dependencies(depMod)(depHead) != null
+        // lift() checks the index, and Option(_) checks for nulls.
+        val valid = dependencies(depMod).lift(depHead).flatMap(Option(_)).isDefined
         val label = if (valid) dependencies(depMod)(depHead).label else "root"
         val head =
           if(generateRelativeHeads) {