Index: poi/src/testcases/org/apache/poi/ss/formula/functions/TestDeltaFunctionsFromSpreadsheet.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- poi/src/testcases/org/apache/poi/ss/formula/functions/TestDeltaFunctionsFromSpreadsheet.java	(revision )
+++ poi/src/testcases/org/apache/poi/ss/formula/functions/TestDeltaFunctionsFromSpreadsheet.java	(revision )
@@ -0,0 +1,31 @@
+/* ====================================================================
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You under the Apache License, Version 2.0
+   (the "License"); you may not use this file except in compliance with
+   the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+==================================================================== */
+
+package org.apache.poi.ss.formula.functions;
+
+/**
+ * Tests DELTA() as loaded from a test data spreadsheet.<p/>
+ *
+ * @author cedric dot walter @ gmail dot com
+ */
+public class TestDeltaFunctionsFromSpreadsheet extends BaseTestFunctionsFromSpreadsheet {
+
+    @Override
+    protected String getFilename() {
+        return "DeltaFunctionTestCaseData.xls";
+    }
+}
\ No newline at end of file
Index: poi/src/java/org/apache/poi/ss/formula/functions/Delta.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- poi/src/java/org/apache/poi/ss/formula/functions/Delta.java	(revision 1488779)
+++ poi/src/java/org/apache/poi/ss/formula/functions/Delta.java	(revision )
@@ -17,6 +17,7 @@
 
 package org.apache.poi.ss.formula.functions;
 
+import org.apache.poi.ss.formula.OperationEvaluationContext;
 import org.apache.poi.ss.formula.eval.*;
 
 import java.math.BigDecimal;
@@ -37,11 +38,14 @@
  *
  * @author cedric dot walter @ gmail dot com
  */
-public final class Delta extends Fixed2ArgFunction {
+public final class Delta extends Fixed2ArgFunction implements FreeRefFunction {
 
+    public static final FreeRefFunction instance = new Delta();
+
     private final static NumberEval ONE = new NumberEval(1);
     private final static NumberEval ZERO = new NumberEval(0);
 
+    @Override
     public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg1, ValueEval arg2) {
         ValueEval veText1;
         try {
@@ -72,4 +76,11 @@
         return result == 0 ? ONE : ZERO;
     }
 
+    @Override
+    public ValueEval evaluate(ValueEval[] args, OperationEvaluationContext ec) {
+        if (args.length != 2) {
+            return ErrorEval.VALUE_INVALID;
+        }
+        return evaluate(ec.getRowIndex(), ec.getColumnIndex(), args[0], args[1]);
+    }
-}
\ No newline at end of file
+}
Index: poi/src/java/org/apache/poi/ss/formula/atp/AnalysisToolPak.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- poi/src/java/org/apache/poi/ss/formula/atp/AnalysisToolPak.java	(revision 1488779)
+++ poi/src/java/org/apache/poi/ss/formula/atp/AnalysisToolPak.java	(revision )
@@ -15,9 +15,7 @@
 import org.apache.poi.ss.formula.eval.ValueEval;
 import org.apache.poi.ss.formula.function.FunctionMetadata;
 import org.apache.poi.ss.formula.function.FunctionMetadataRegistry;
-import org.apache.poi.ss.formula.functions.EDate;
-import org.apache.poi.ss.formula.functions.FreeRefFunction;
-import org.apache.poi.ss.formula.functions.Sumifs;
+import org.apache.poi.ss.formula.functions.*;
 import org.apache.poi.ss.formula.udf.UDFFinder;
 
 import java.util.*;
@@ -72,9 +70,9 @@
         r(m, "BESSELK", null);
         r(m, "BESSELY", null);
         r(m, "BIN2DEC", null);
-        r(m, "BIN2HEX", null);
+        r(m, "BIN2HEX", Bin2Hex.instance);
         r(m, "BIN2OCT", null);
-        r(m, "COMPLEX", null);
+        r(m, "COMPLEX", Complex.instance);
         r(m, "CONVERT", null);
         r(m, "COUNTIFS", null);
         r(m, "COUPDAYBS", null);
@@ -93,9 +91,9 @@
         r(m, "CUMIPMT", null);
         r(m, "CUMPRINC", null);
         r(m, "DEC2BIN", null);
-        r(m, "DEC2HEX", null);
+        r(m, "DEC2HEX", Dec2Hex.instance);
         r(m, "DEC2OCT", null);
-        r(m, "DELTA", null);
+        r(m, "DELTA", Delta.instance);
         r(m, "DISC", null);
         r(m, "DOLLARDE", null);
         r(m, "DOLLARFR", null);
@@ -150,7 +148,7 @@
         r(m, "PRICE", null);
         r(m, "PRICEDISC", null);
         r(m, "PRICEMAT", null);
-        r(m, "QUOTIENT", null);
+        r(m, "QUOTIENT", Quotient.instance);
         r(m, "RANDBETWEEN", RandBetween.instance);
         r(m, "RECEIVED", null);
         r(m, "RTD", null);