1 files changed, 63 insertions, 0 deletions
diff --git a/src/de/lmu/ifi/dbs/elki/distance/distancefunction/set/AbstractSetDistanceFunction.java b/src/de/lmu/ifi/dbs/elki/distance/distancefunction/set/AbstractSetDistanceFunction.java
new file mode 100644
index 00000000..5f374c78
--- /dev/null
+++ b/src/de/lmu/ifi/dbs/elki/distance/distancefunction/set/AbstractSetDistanceFunction.java
@@ -0,0 +1,63 @@
+package de.lmu.ifi.dbs.elki.distance.distancefunction.set;
+
+/*
+ This file is part of ELKI:
+ Environment for Developing KDD-Applications Supported by Index-Structures
+
+ Copyright (C) 2014
+ Ludwig-Maximilians-Universität München
+ Lehr- und Forschungseinheit für Datenbanksysteme
+ ELKI Development Team
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU Affero General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ GNU Affero General Public License for more details.
+
+ You should have received a copy of the GNU Affero General Public License
+ along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+import de.lmu.ifi.dbs.elki.data.FeatureVector;
+import de.lmu.ifi.dbs.elki.distance.distancefunction.AbstractPrimitiveDistanceFunction;
+
+/**
+ * Abstract base class for set distance functions.
+ * 
+ * @author Erich Schubert
+ *
+ * @param <O> Vector type
+ */
+public abstract class AbstractSetDistanceFunction<O> extends AbstractPrimitiveDistanceFunction<O> {
+  /**
+   * Constants for checking null.
+   */
+  public static final Integer INTEGER_NULL = Integer.valueOf(0);
+
+  /**
+   * Constants for checking null.
+   */
+  public static final Double DOUBLE_NULL = Double.valueOf(0.);
+
+  /**
+   * Empty string.
+   */
+  public static final String STRING_NULL = "";
+
+  /**
+   * Test a value for null.
+   * 
+   * TODO: delegate to {@link FeatureVector} instead?
+   * 
+   * @param val Value
+   * @return true when null
+   */
+  protected static boolean isNull(Object val) {
+    return (val == null) || STRING_NULL.equals(val) || DOUBLE_NULL.equals(val) || INTEGER_NULL.equals(val);
+  }
+}