1 files changed, 61 insertions, 0 deletions

diff --git a/subprojects/viatra-runtime-matchers/src/main/java/tools/refinery/viatra/runtime/matchers/util/Direction.java b/subprojects/viatra-runtime-matchers/src/main/java/tools/refinery/viatra/runtime/matchers/util/Direction.java
new file mode 100644
index 00000000..88f7ec00
--- /dev/null
+++ b/subprojects/viatra-runtime-matchers/src/main/java/tools/refinery/viatra/runtime/matchers/util/Direction.java
@@ -0,0 +1,61 @@
+/*******************************************************************************
+ * Copyright (c) 2010-2019, Tamas Szabo, itemis AG, Gabor Bergmann, IncQuery Labs 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.util;
+
+/**
+ * Indicates whether a propagated update event signals the insertion or deletion of an element
+ * 
+ * @author Gabor Bergmann
+ */
+public enum Direction {
+    INSERT, DELETE;
+
+    /**
+     * @since 2.4
+     */
+    public Direction opposite() {
+        switch (this) {
+        case INSERT:
+            return DELETE;
+        default:
+            return INSERT;
+        }
+    }
+
+    /**
+     * @since 2.4
+     */
+    public char asSign() {
+        switch (this) {
+        case INSERT:
+            return '+';
+        default:
+            return '-';
+        }
+    }
+    
+    /**
+     * Returns the direction that is the product of this direction and the other direction.
+     *  
+     * DELETE x DELETE = INSERT
+     * DELETE x INSERT = DELETE
+     * INSERT x DELETE = DELETE
+     * INSERT x INSERT = INSERT 
+     * @since 2.4
+     */
+    public Direction multiply(final Direction other) {
+        switch (this) {
+        case DELETE:
+            return other.opposite();
+        default:
+            return other;
+        }
+    }
+    
+}