From 5a55d0d306e85a697aa86bdf3f9caf243d384faa Mon Sep 17 00:00:00 2001
From: Kristóf Marussy <kris7topher@gmail.com>
Date: Fri, 10 May 2019 00:01:57 -0400
Subject: Neutral element for sum is [0, 0]

---
 .../logic2viatra/interval/IntervalAggregationMode.java           | 9 +++++++++
 .../logic2viatra/interval/IntervalAggregationOperator.xtend      | 4 ++--
 2 files changed, 11 insertions(+), 2 deletions(-)

(limited to 'Solvers/VIATRA-Solver/hu.bme.mit.inf.dslreasoner.viatrasolver.logic2viatra/src/hu/bme/mit/inf/dslreasoner')

diff --git a/Solvers/VIATRA-Solver/hu.bme.mit.inf.dslreasoner.viatrasolver.logic2viatra/src/hu/bme/mit/inf/dslreasoner/viatrasolver/logic2viatra/interval/IntervalAggregationMode.java b/Solvers/VIATRA-Solver/hu.bme.mit.inf.dslreasoner.viatrasolver.logic2viatra/src/hu/bme/mit/inf/dslreasoner/viatrasolver/logic2viatra/interval/IntervalAggregationMode.java
index f5bd2efc..66dcb00f 100644
--- a/Solvers/VIATRA-Solver/hu.bme.mit.inf.dslreasoner.viatrasolver.logic2viatra/src/hu/bme/mit/inf/dslreasoner/viatrasolver/logic2viatra/interval/IntervalAggregationMode.java
+++ b/Solvers/VIATRA-Solver/hu.bme.mit.inf.dslreasoner.viatrasolver.logic2viatra/src/hu/bme/mit/inf/dslreasoner/viatrasolver/logic2viatra/interval/IntervalAggregationMode.java
@@ -21,6 +21,11 @@ public enum IntervalAggregationMode implements BinaryOperator<Interval> {
 				}
 			};
 		}
+		
+		@Override
+		public Interval getNeutral() {
+			return Interval.ZERO;
+		}
 	},
 
 	JOIN("intervalJoin", "Calculate the smallest interval containing all the intervals in a set") {
@@ -63,4 +68,8 @@ public enum IntervalAggregationMode implements BinaryOperator<Interval> {
 	}
 
 	public abstract IntervalRedBlackNode createNode(Interval interval);
+	
+	public Interval getNeutral() {
+		return Interval.EMPTY;
+	}
 }
diff --git a/Solvers/VIATRA-Solver/hu.bme.mit.inf.dslreasoner.viatrasolver.logic2viatra/src/hu/bme/mit/inf/dslreasoner/viatrasolver/logic2viatra/interval/IntervalAggregationOperator.xtend b/Solvers/VIATRA-Solver/hu.bme.mit.inf.dslreasoner.viatrasolver.logic2viatra/src/hu/bme/mit/inf/dslreasoner/viatrasolver/logic2viatra/interval/IntervalAggregationOperator.xtend
index 940c71bb..21d3d73b 100644
--- a/Solvers/VIATRA-Solver/hu.bme.mit.inf.dslreasoner.viatrasolver.logic2viatra/src/hu/bme/mit/inf/dslreasoner/viatrasolver/logic2viatra/interval/IntervalAggregationOperator.xtend
+++ b/Solvers/VIATRA-Solver/hu.bme.mit.inf.dslreasoner.viatrasolver.logic2viatra/src/hu/bme/mit/inf/dslreasoner/viatrasolver/logic2viatra/interval/IntervalAggregationOperator.xtend
@@ -36,13 +36,13 @@ class IntervalAggregationOperator implements IMultisetAggregationOperator<Interv
 
 	override getAggregate(IntervalRedBlackNode result) {
 		if (result.leaf) {
-			null
+			mode.neutral
 		} else {
 			result.result
 		}
 	}
 
 	override aggregateStream(Stream<Interval> stream) {
-		stream.reduce(mode).orElse(null)
+		stream.reduce(mode).orElse(mode.neutral)
 	}
 }
-- 
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