1 files changed, 61 insertions, 0 deletions

diff --git a/subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/matchers/aggregators/LongSumOperator.java b/subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/matchers/aggregators/LongSumOperator.java
new file mode 100644
index 00000000..29ded090
--- /dev/null
+++ b/subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/matchers/aggregators/LongSumOperator.java
@@ -0,0 +1,61 @@
+/*******************************************************************************
+ * Copyright (c) 2010-2016, Gabor Bergmann, IncQueryLabs Ltd.
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-v20.html.
+ * 
+ * SPDX-License-Identifier: EPL-2.0
+ *******************************************************************************/
+package tools.refinery.viatra.runtime.matchers.aggregators;
+
+import java.util.stream.Stream;
+
+import tools.refinery.viatra.runtime.matchers.psystem.aggregations.AbstractMemorylessAggregationOperator;
+
+/**
+ * Incrementally computes the sum of java.lang.Long values
+ * @author Gabor Bergmann
+ * @since 1.4
+ */
+public class LongSumOperator extends AbstractMemorylessAggregationOperator<Long, Long> {
+    public static final LongSumOperator INSTANCE = new LongSumOperator();
+    
+    private LongSumOperator() {
+        // Singleton, do not call.
+    }
+
+    @Override
+    public String getShortDescription() {
+        return "sum<Long> incrementally computes the sum of java.lang.Long values";
+    }
+    @Override
+    public String getName() {
+        return "sum<Long>";
+    }
+    
+    @Override
+    public Long createNeutral() {
+        return 0L;
+    }
+
+    @Override
+    public boolean isNeutral(Long result) {
+        return createNeutral().equals(result);
+    }
+
+    @Override
+    public Long update(Long oldResult, Long updateValue, boolean isInsertion) {
+        return isInsertion ? 
+                oldResult + updateValue : 
+                oldResult - updateValue;
+    }
+
+    /**
+     * @since 2.0
+     */
+    @Override
+    public Long aggregateStream(Stream<Long> stream) {
+        return stream.mapToLong(Long::longValue).sum();
+    }
+    
+}