1 files changed, 93 insertions, 0 deletions

diff --git a/subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/matchers/util/EmptyMemory.java b/subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/matchers/util/EmptyMemory.java
new file mode 100644
index 00000000..a17b3a3f
--- /dev/null
+++ b/subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/matchers/util/EmptyMemory.java
@@ -0,0 +1,93 @@
+/*******************************************************************************
+ * Copyright (c) 2010-2018, 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;
+
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.Set;
+
+/**
+ * A singleton immutable empty memory. 
+ * @author Gabor Bergmann
+ * @since 2.0
+ *
+ */
+public class EmptyMemory<T> implements IMemoryView<T> {
+
+    @SuppressWarnings("rawtypes")
+    private static final EmptyMemory INSTANCE = new EmptyMemory();
+    
+    @SuppressWarnings("unchecked")
+    public static <T> EmptyMemory<T> instance() {
+        return INSTANCE;
+    }
+    
+    
+    
+    /**
+     * Singleton; hidden constructor
+     */
+    private EmptyMemory() {
+        super();
+    }
+
+    @Override
+    public Iterator<T> iterator() {
+        return Collections.<T>emptySet().iterator();
+    }
+
+    @Override
+    public int getCount(T value) {
+        return 0;
+    }
+
+    @Override
+    public int getCountUnsafe(Object value) {
+        return 0;
+    }
+
+    @Override
+    public boolean containsNonZero(T value) {
+        return false;
+    }
+
+    @Override
+    public boolean containsNonZeroUnsafe(Object value) {
+        return false;
+    }
+
+    @Override
+    public int size() {
+        return 0;
+    }
+
+    @Override
+    public boolean isEmpty() {
+        return true;
+    }
+
+    @Override
+    public Set<T> distinctValues() {
+        return Collections.emptySet();
+    }
+    
+    @Override
+    public int hashCode() {
+        return IMemoryView.hashCode(this);
+    }
+    @Override
+    public boolean equals(Object obj) {
+        return IMemoryView.equals(this, obj);
+    }
+
+    @Override
+    public String toString() {
+        return "{}";
+    }
+}