1 files changed, 30 insertions, 0 deletions

diff --git a/subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/matchers/util/IMultiset.java b/subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/matchers/util/IMultiset.java
new file mode 100644
index 00000000..bdd5d597
--- /dev/null
+++ b/subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/matchers/util/IMultiset.java
@@ -0,0 +1,30 @@
+/*******************************************************************************
+ * Copyright (c) 2010-2017, 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.util;
+
+/**
+ * An {@link IMemory} that always contains values with a nonnegative multiplicity.
+ * 
+ * <p> In case a write operation caused underflow, an {@link IllegalStateException} is thrown.
+ * 
+ * @author Gabor Bergmann
+ * @since 1.7
+ */
+public interface IMultiset<T> extends IMemory<T> {
+
+    /**
+     * Adds the given number of occurrences to the memory. The count value must be a positive number.
+     * 
+     * @param count
+     *            the number of occurrences
+     * @return true if the tuple was not present before in the memory
+     */
+    boolean addPositive(T value, int count);
+    
+}
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