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diff --git a/subprojects/viatra-runtime-localsearch/src/main/java/tools/refinery/viatra/runtime/localsearch/operations/ExtendOperationExecutor.java b/subprojects/viatra-runtime-localsearch/src/main/java/tools/refinery/viatra/runtime/localsearch/operations/ExtendOperationExecutor.java
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index 00000000..a72c30dd
--- /dev/null
+++ b/subprojects/viatra-runtime-localsearch/src/main/java/tools/refinery/viatra/runtime/localsearch/operations/ExtendOperationExecutor.java
@@ -0,0 +1,77 @@
+/*******************************************************************************
+ * Copyright (c) 2010-2013, Zoltan Ujhelyi, Akos Horvath, Istvan Rath and Daniel Varro
+ * Copyright (c) 2023 The Refinery Authors <https://refinery.tools/>
+ * 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.localsearch.operations;
+
+import tools.refinery.viatra.runtime.localsearch.MatchingFrame;
+import tools.refinery.viatra.runtime.localsearch.matcher.ISearchContext;
+import tools.refinery.viatra.runtime.localsearch.operations.ISearchOperation.ISearchOperationExecutor;
+
+import java.util.Iterator;
+
+/**
+ * An operation that can be used to enumerate all possible values for a single position based on a constraint
+ * @author Zoltan Ujhelyi, Akos Horvath
+ * @noextend This class is not intended to be subclassed by clients.
+ * @since 2.0
+ */
+public abstract class ExtendOperationExecutor<T> implements ISearchOperationExecutor {
+
+    private Iterator<? extends T> it;
+
+    /**
+     * Returns an iterator with the possible options from the current state
+     * @since 2.0
+     */
+    protected abstract Iterator<? extends T> getIterator(MatchingFrame frame, ISearchContext context);
+    /**
+     * Updates the frame with the next element of the iterator. Called during {@link #execute(MatchingFrame, ISearchContext)}.
+     *
+     * @return true if the update is successful or false otherwise; in case of false is returned, the next element should be taken from the iterator.
+     * @since 2.0
+     */
+    protected abstract boolean fillInValue(T newValue, MatchingFrame frame, ISearchContext context);
+
+    /**
+     * Restores the frame to the state before {@link #fillInValue(Object, MatchingFrame, ISearchContext)}. Called during
+     * {@link #onBacktrack(MatchingFrame, ISearchContext)}.
+     *
+     * @since 2.0
+     */
+    protected abstract void cleanup(MatchingFrame frame, ISearchContext context);
+
+    @Override
+    public void onInitialize(MatchingFrame frame, ISearchContext context) {
+        it = getIterator(frame, context);
+    }
+
+    @Override
+    public void onBacktrack(MatchingFrame frame, ISearchContext context) {
+        it = null;
+
+    }
+
+        /**
+         * Fixed version that handles failed unification of variables correctly.
+         * @param frame The matching frame to extend.
+         * @param context The search context.
+         * @return {@code true} if an extension was found, {@code false} otherwise.
+         */
+        @Override
+        public boolean execute(MatchingFrame frame, ISearchContext context) {
+                while (it.hasNext()) {
+                        var newValue = it.next();
+                        if (fillInValue(newValue, frame, context)) {
+                                return true;
+                        }
+                }
+                return false;
+        }
+
+}