added fixed arg function interfaces, converted some functions

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@883045 13f79535-47bb-0310-9956-ffa450edef68

37 files changed, 524 insertions, 270 deletions

diff --git a/src/java/org/apache/poi/hssf/record/formula/eval/ConcatEval.java b/src/java/org/apache/poi/hssf/record/formula/eval/ConcatEval.java
index 0db4994b59..53d8c7bc29 100644
--- a/src/java/org/apache/poi/hssf/record/formula/eval/ConcatEval.java
+++ b/src/java/org/apache/poi/hssf/record/formula/eval/ConcatEval.java
@@ -17,12 +17,13 @@
 
 package org.apache.poi.hssf.record.formula.eval;
 
+import org.apache.poi.hssf.record.formula.functions.Fixed2ArgFunction;
 import org.apache.poi.hssf.record.formula.functions.Function;
 
 /**
  * @author Amol S. Deshmukh < amolweb at ya hoo dot com >
  */
-public final class ConcatEval implements Function {
+public final class ConcatEval  extends Fixed2ArgFunction {
 
 	public static final Function instance = new ConcatEval();
 
@@ -30,29 +31,30 @@ public final class ConcatEval implements Function {
 		// enforce singleton
 	}
 
-	public ValueEval evaluate(ValueEval[] args, int srcRow, int srcCol) {
-		if(args.length != 2) {
-			return ErrorEval.VALUE_INVALID;
-		}
-		StringBuffer sb = new StringBuffer();
+	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0, ValueEval arg1) {
+		ValueEval ve0;
+		ValueEval ve1;
 		try {
-			for (int i = 0; i < 2; i++) {
-
-				ValueEval ve = OperandResolver.getSingleValue(args[i], srcRow, srcCol);
-				if (ve instanceof StringValueEval) {
-					StringValueEval sve = (StringValueEval) ve;
-					sb.append(sve.getStringValue());
-				} else if (ve == BlankEval.INSTANCE) {
-					// do nothing
-				} else {
-					throw new RuntimeException("Unexpected value type ("
-							+ ve.getClass().getName() + ")");
-				}
-			}
+			ve0 = OperandResolver.getSingleValue(arg0, srcRowIndex, srcColumnIndex);
+			ve1 = OperandResolver.getSingleValue(arg1, srcRowIndex, srcColumnIndex);
 		} catch (EvaluationException e) {
 			return e.getErrorEval();
 		}
-
+		StringBuilder sb = new StringBuilder();
+		sb.append(getText(ve0));
+		sb.append(getText(ve1));
 		return new StringEval(sb.toString());
 	}
+
+	private Object getText(ValueEval ve) {
+		if (ve instanceof StringValueEval) {
+			StringValueEval sve = (StringValueEval) ve;
+			return sve.getStringValue();
+		}
+		if (ve == BlankEval.INSTANCE) {
+			return "";
+		}
+		throw new IllegalAccessError("Unexpected value type ("
+					+ ve.getClass().getName() + ")");
+	}
 }
diff --git a/src/java/org/apache/poi/hssf/record/formula/eval/IntersectionEval.java b/src/java/org/apache/poi/hssf/record/formula/eval/IntersectionEval.java
index b208bcd647..e30df36f59 100644
--- a/src/java/org/apache/poi/hssf/record/formula/eval/IntersectionEval.java
+++ b/src/java/org/apache/poi/hssf/record/formula/eval/IntersectionEval.java
@@ -17,12 +17,13 @@
 
 package org.apache.poi.hssf.record.formula.eval;
 
+import org.apache.poi.hssf.record.formula.functions.Fixed2ArgFunction;
 import org.apache.poi.hssf.record.formula.functions.Function;
 
 /**
  * @author Josh Micich
  */
-public final class IntersectionEval implements Function {
+public final class IntersectionEval  extends Fixed2ArgFunction {
 
 	public static final Function instance = new IntersectionEval();
 
@@ -30,14 +31,11 @@ public final class IntersectionEval implements Function {
 		// enforces singleton
 	}
 
-	public ValueEval evaluate(ValueEval[] args, int srcRow, int srcCol) {
-		if(args.length != 2) {
-			return ErrorEval.VALUE_INVALID;
-		}
+	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0, ValueEval arg1) {
 
 		try {
-			AreaEval reA = evaluateRef(args[0]);
-			AreaEval reB = evaluateRef(args[1]);
+			AreaEval reA = evaluateRef(arg0);
+			AreaEval reB = evaluateRef(arg1);
 			AreaEval result = resolveRange(reA, reB);
 			if (result == null) {
 				return ErrorEval.NULL_INTERSECTION;
diff --git a/src/java/org/apache/poi/hssf/record/formula/eval/PercentEval.java b/src/java/org/apache/poi/hssf/record/formula/eval/PercentEval.java
index 0d509cc438..93db027b30 100644
--- a/src/java/org/apache/poi/hssf/record/formula/eval/PercentEval.java
+++ b/src/java/org/apache/poi/hssf/record/formula/eval/PercentEval.java
@@ -17,6 +17,7 @@
 
 package org.apache.poi.hssf.record.formula.eval;
 
+import org.apache.poi.hssf.record.formula.functions.Fixed1ArgFunction;
 import org.apache.poi.hssf.record.formula.functions.Function;
 
 
@@ -24,7 +25,7 @@ import org.apache.poi.hssf.record.formula.functions.Function;
  * Implementation of Excel formula token '%'. <p/>
  * @author Josh Micich
  */
-public final class PercentEval implements Function {
+public final class PercentEval extends Fixed1ArgFunction {
 
 	public static final Function instance = new PercentEval();
 
@@ -32,13 +33,10 @@ public final class PercentEval implements Function {
 		// enforce singleton
 	}
 
-	public ValueEval evaluate(ValueEval[] args, int srcRow, int srcCol) {
-		if (args.length != 1) {
-			return ErrorEval.VALUE_INVALID;
-		}
+	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0) {
 		double d;
 		try {
-			ValueEval ve = OperandResolver.getSingleValue(args[0], srcRow, srcCol);
+			ValueEval ve = OperandResolver.getSingleValue(arg0, srcRowIndex, srcColumnIndex);
 			d = OperandResolver.coerceValueToDouble(ve);
 		} catch (EvaluationException e) {
 			return e.getErrorEval();
diff --git a/src/java/org/apache/poi/hssf/record/formula/eval/RangeEval.java b/src/java/org/apache/poi/hssf/record/formula/eval/RangeEval.java
index bd821f0acb..6a8186c7b7 100644
--- a/src/java/org/apache/poi/hssf/record/formula/eval/RangeEval.java
+++ b/src/java/org/apache/poi/hssf/record/formula/eval/RangeEval.java
@@ -17,6 +17,7 @@
 
 package org.apache.poi.hssf.record.formula.eval;
 
+import org.apache.poi.hssf.record.formula.functions.Fixed2ArgFunction;
 import org.apache.poi.hssf.record.formula.functions.Function;
 
 
@@ -24,7 +25,7 @@ import org.apache.poi.hssf.record.formula.functions.Function;
  *
  * @author Josh Micich
  */
-public final class RangeEval implements Function {
+public final class RangeEval extends Fixed2ArgFunction {
 
 	public static final Function instance = new RangeEval();
 
@@ -32,14 +33,11 @@ public final class RangeEval implements Function {
 		// enforces singleton
 	}
 
-	public ValueEval evaluate(ValueEval[] args, int srcRow, int srcCol) {
-		if(args.length != 2) {
-			return ErrorEval.VALUE_INVALID;
-		}
+	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0, ValueEval arg1) {
 
 		try {
-			AreaEval reA = evaluateRef(args[0]);
-			AreaEval reB = evaluateRef(args[1]);
+			AreaEval reA = evaluateRef(arg0);
+			AreaEval reB = evaluateRef(arg1);
 			return resolveRange(reA, reB);
 		} catch (EvaluationException e) {
 			return e.getErrorEval();
diff --git a/src/java/org/apache/poi/hssf/record/formula/eval/RelationalOperationEval.java b/src/java/org/apache/poi/hssf/record/formula/eval/RelationalOperationEval.java
index 35cf5b4347..63b68c441a 100644
--- a/src/java/org/apache/poi/hssf/record/formula/eval/RelationalOperationEval.java
+++ b/src/java/org/apache/poi/hssf/record/formula/eval/RelationalOperationEval.java
@@ -17,6 +17,7 @@
 
 package org.apache.poi.hssf.record.formula.eval;
 
+import org.apache.poi.hssf.record.formula.functions.Fixed2ArgFunction;
 import org.apache.poi.hssf.record.formula.functions.Function;
 import org.apache.poi.ss.util.NumberComparer;
 
@@ -25,7 +26,7 @@ import org.apache.poi.ss.util.NumberComparer;
  *
  * @author Amol S. Deshmukh &lt; amolweb at ya hoo dot com &gt;
  */
-public abstract class RelationalOperationEval implements Function {
+public abstract class RelationalOperationEval extends Fixed2ArgFunction {
 
 	/**
 	 * Converts a standard compare result (-1, 0, 1) to <code>true</code> or <code>false</code>
@@ -55,16 +56,13 @@ public abstract class RelationalOperationEval implements Function {
 	 * Blank < Positive numbers
 	 * </pre>
 	 */
-	public final ValueEval evaluate(ValueEval[] operands, int srcRow, int srcCol) {
-		if (operands.length != 2) {
-			return ErrorEval.VALUE_INVALID;
-		}
+	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0, ValueEval arg1) {
 
 		ValueEval vA;
 		ValueEval vB;
 		try {
-			vA = OperandResolver.getSingleValue(operands[0], srcRow, srcCol);
-			vB = OperandResolver.getSingleValue(operands[1], srcRow, srcCol);
+			vA = OperandResolver.getSingleValue(arg0, srcRowIndex, srcColumnIndex);
+			vB = OperandResolver.getSingleValue(arg1, srcRowIndex, srcColumnIndex);
 		} catch (EvaluationException e) {
 			return e.getErrorEval();
 		}
diff --git a/src/java/org/apache/poi/hssf/record/formula/eval/TwoOperandNumericOperation.java b/src/java/org/apache/poi/hssf/record/formula/eval/TwoOperandNumericOperation.java
index 1584e17bba..7e6ac88364 100644
--- a/src/java/org/apache/poi/hssf/record/formula/eval/TwoOperandNumericOperation.java
+++ b/src/java/org/apache/poi/hssf/record/formula/eval/TwoOperandNumericOperation.java
@@ -17,23 +17,23 @@
 
 package org.apache.poi.hssf.record.formula.eval;
 
+import org.apache.poi.hssf.record.formula.functions.Fixed2ArgFunction;
 import org.apache.poi.hssf.record.formula.functions.Function;
 
 /**
  * @author Josh Micich
  */
-public abstract class TwoOperandNumericOperation implements Function {
+public abstract class TwoOperandNumericOperation extends Fixed2ArgFunction {
 
 	protected final double singleOperandEvaluate(ValueEval arg, int srcCellRow, int srcCellCol) throws EvaluationException {
 		ValueEval ve = OperandResolver.getSingleValue(arg, srcCellRow, srcCellCol);
 		return OperandResolver.coerceValueToDouble(ve);
 	}
-
-	public final ValueEval evaluate(ValueEval[] args, int srcCellRow, int srcCellCol) {
+	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0, ValueEval arg1) {
 		double result;
 		try {
-			double d0 = singleOperandEvaluate(args[0], srcCellRow, srcCellCol);
-			double d1 = singleOperandEvaluate(args[1], srcCellRow, srcCellCol);
+			double d0 = singleOperandEvaluate(arg0, srcRowIndex, srcColumnIndex);
+			double d1 = singleOperandEvaluate(arg1, srcRowIndex, srcColumnIndex);
 			result = evaluate(d0, d1);
 			if (result == 0.0) { // this '==' matches +0.0 and -0.0
 				// Excel converts -0.0 to +0.0 for '*', '/', '%', '+' and '^'
@@ -49,6 +49,7 @@ public abstract class TwoOperandNumericOperation implements Function {
 		}
 		return new NumberEval(result);
 	}
+
 	protected abstract double evaluate(double d0, double d1) throws EvaluationException;
 
 	public static final Function AddEval = new TwoOperandNumericOperation() {
diff --git a/src/java/org/apache/poi/hssf/record/formula/eval/UnaryMinusEval.java b/src/java/org/apache/poi/hssf/record/formula/eval/UnaryMinusEval.java
index 0d87ab036a..ba5f197dce 100644
--- a/src/java/org/apache/poi/hssf/record/formula/eval/UnaryMinusEval.java
+++ b/src/java/org/apache/poi/hssf/record/formula/eval/UnaryMinusEval.java
@@ -17,14 +17,13 @@
 
 package org.apache.poi.hssf.record.formula.eval;
 
+import org.apache.poi.hssf.record.formula.functions.Fixed1ArgFunction;
 import org.apache.poi.hssf.record.formula.functions.Function;
 
-
 /**
  * @author Amol S. Deshmukh &lt; amolweb at ya hoo dot com &gt;
- *
  */
-public final class UnaryMinusEval implements Function {
+public final class UnaryMinusEval extends Fixed1ArgFunction {
 
 	public static final Function instance = new UnaryMinusEval();
 
@@ -32,13 +31,10 @@ public final class UnaryMinusEval implements Function {
 		// enforce singleton
 	}
 
-	public ValueEval evaluate(ValueEval[] args, int srcRow, int srcCol) {
-		if (args.length != 1) {
-			return ErrorEval.VALUE_INVALID;
-		}
+	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0) {
 		double d;
 		try {
-			ValueEval ve = OperandResolver.getSingleValue(args[0], srcRow, srcCol);
+			ValueEval ve = OperandResolver.getSingleValue(arg0, srcRowIndex, srcColumnIndex);
 			d = OperandResolver.coerceValueToDouble(ve);
 		} catch (EvaluationException e) {
 			return e.getErrorEval();
diff --git a/src/java/org/apache/poi/hssf/record/formula/eval/UnaryPlusEval.java b/src/java/org/apache/poi/hssf/record/formula/eval/UnaryPlusEval.java
index e2b137b4b3..b6f32e9b61 100644
--- a/src/java/org/apache/poi/hssf/record/formula/eval/UnaryPlusEval.java
+++ b/src/java/org/apache/poi/hssf/record/formula/eval/UnaryPlusEval.java
@@ -17,14 +17,14 @@
 
 package org.apache.poi.hssf.record.formula.eval;
 
+import org.apache.poi.hssf.record.formula.functions.Fixed1ArgFunction;
 import org.apache.poi.hssf.record.formula.functions.Function;
 
 
 /**
  * @author Amol S. Deshmukh &lt; amolweb at ya hoo dot com &gt;
- *
  */
-public final class UnaryPlusEval implements Function {
+public final class UnaryPlusEval extends Fixed1ArgFunction {
 
 	public static final Function instance = new UnaryPlusEval();
 
@@ -32,13 +32,10 @@ public final class UnaryPlusEval implements Function {
 		// enforce singleton
 	}
 
-	public ValueEval evaluate(ValueEval[] args, int srcCellRow, int srcCellCol) {
-		if(args.length != 1) {
-			return ErrorEval.VALUE_INVALID;
-		}
+	public ValueEval evaluate(int srcCellRow, int srcCellCol, ValueEval arg0) {
 		double d;
 		try {
-			ValueEval ve = OperandResolver.getSingleValue(args[0], srcCellRow, srcCellCol);
+			ValueEval ve = OperandResolver.getSingleValue(arg0, srcCellRow, srcCellCol);
 			if(ve instanceof StringEval) {
 				// Note - asymmetric with UnaryMinus
 				// -"hello" evaluates to #VALUE!
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/CalendarFieldFunction.java b/src/java/org/apache/poi/hssf/record/formula/functions/CalendarFieldFunction.java
index a4c445aa55..3261f209be 100644
--- a/src/java/org/apache/poi/hssf/record/formula/functions/CalendarFieldFunction.java
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/CalendarFieldFunction.java
@@ -34,7 +34,7 @@ import org.apache.poi.hssf.usermodel.HSSFDateUtil;
  *
  * @author Guenter Kickinger g.kickinger@gmx.net
  */
-public final class CalendarFieldFunction implements Function {
+public final class CalendarFieldFunction extends Fixed1ArgFunction {
 
 	public static final Function YEAR = new CalendarFieldFunction(Calendar.YEAR, false);
 	public static final Function MONTH = new CalendarFieldFunction(Calendar.MONTH, true);
@@ -48,14 +48,10 @@ public final class CalendarFieldFunction implements Function {
 		_needsOneBaseAdjustment = needsOneBaseAdjustment;
 	}
 
-	public ValueEval evaluate(ValueEval[] operands, int srcCellRow, int srcCellCol) {
-		if (operands.length != 1) {
-			return ErrorEval.VALUE_INVALID;
-		}
-
+	public final ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0) {
 		int val;
 		try {
-			ValueEval ve = OperandResolver.getSingleValue(operands[0], srcCellRow, srcCellCol);
+			ValueEval ve = OperandResolver.getSingleValue(arg0, srcRowIndex, srcColumnIndex);
 			val = OperandResolver.coerceValueToInt(ve);
 		} catch (EvaluationException e) {
 			return e.getErrorEval();
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/Column.java b/src/java/org/apache/poi/hssf/record/formula/functions/Column.java
index e984cc2c7b..02a34b4e27 100644
--- a/src/java/org/apache/poi/hssf/record/formula/functions/Column.java
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/Column.java
@@ -23,39 +23,32 @@ import org.apache.poi.hssf.record.formula.eval.NumberEval;
 import org.apache.poi.hssf.record.formula.eval.RefEval;
 import org.apache.poi.hssf.record.formula.eval.ValueEval;
 
-public final class Column implements Function {
-    public ValueEval evaluate(ValueEval[] evals, int srcCellRow, int srcCellCol) {
-        ValueEval retval = null;
-        int cnum = -1;
-
-        switch (evals.length) {
-        default:
-            retval = ErrorEval.VALUE_INVALID;
-        case 1:
-            if (evals[0] instanceof AreaEval) {
-                AreaEval ae = (AreaEval) evals[0];
-                cnum = ae.getFirstColumn();
-            }
-            else if (evals[0] instanceof RefEval) {
-                RefEval re = (RefEval) evals[0];
-                cnum = re.getColumn();
-            }
-            else { // anything else is not valid argument
-                retval = ErrorEval.VALUE_INVALID;
-            }
-            break;
-        case 0:
-            cnum = srcCellCol;
-        }
+public final class Column implements Function0Arg, Function1Arg {
 
-        if (retval == null) {
-            retval = (cnum >= 0)
-                    ? new NumberEval(cnum + 1) // +1 since excel colnums are 1 based
-                    : (ValueEval) ErrorEval.VALUE_INVALID;
+    public ValueEval evaluate(int srcRowIndex, int srcColumnIndex) {
+        return new NumberEval(srcColumnIndex+1);
+    }
+    public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0) {
+        int rnum;
+
+        if (arg0 instanceof AreaEval) {
+            rnum = ((AreaEval) arg0).getFirstColumn();
+        } else if (arg0 instanceof RefEval) {
+            rnum = ((RefEval) arg0).getColumn();
+        } else {
+            // anything else is not valid argument
+            return ErrorEval.VALUE_INVALID;
         }
 
-        return retval;
+        return new NumberEval(rnum + 1);
+    }
+    public ValueEval evaluate(ValueEval[] args, int srcRowIndex, int srcColumnIndex) {
+        switch (args.length) {
+            case 1:
+                return evaluate(srcRowIndex, srcColumnIndex, args[0]);
+            case 0:
+                return new NumberEval(srcColumnIndex+1);
+        }
+        return ErrorEval.VALUE_INVALID;
     }
-
-
 }
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/Columns.java b/src/java/org/apache/poi/hssf/record/formula/functions/Columns.java
index ca0e97f305..0ef7e06324 100644
--- a/src/java/org/apache/poi/hssf/record/formula/functions/Columns.java
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/Columns.java
@@ -28,27 +28,14 @@ import org.apache.poi.hssf.record.formula.eval.ValueEval;
  *
  * @author Josh Micich
  */
-public final class Columns implements Function {
+public final class Columns extends Fixed1ArgFunction {
 
-	public ValueEval evaluate(ValueEval[] args, int srcCellRow, int srcCellCol) {
-		switch(args.length) {
-			case 1:
-				// expected
-				break;
-			case 0:
-				// too few arguments
-				return ErrorEval.VALUE_INVALID;
-			default:
-				// too many arguments
-				return ErrorEval.VALUE_INVALID;
-		}
-		ValueEval firstArg = args[0];
+	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0) {
 
 		int result;
-		if (firstArg instanceof AreaEval) {
-			AreaEval ae = (AreaEval) firstArg;
-			result = ae.getLastColumn() - ae.getFirstColumn() + 1;
-		} else if (firstArg instanceof RefEval) {
+		if (arg0 instanceof AreaEval) {
+			result = ((AreaEval) arg0).getWidth();
+		} else if (arg0 instanceof RefEval) {
 			result = 1;
 		} else { // anything else is not valid argument
 			return ErrorEval.VALUE_INVALID;
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/Countblank.java b/src/java/org/apache/poi/hssf/record/formula/functions/Countblank.java
index 473976e330..a668225da4 100644
--- a/src/java/org/apache/poi/hssf/record/formula/functions/Countblank.java
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/Countblank.java
@@ -19,7 +19,6 @@ package org.apache.poi.hssf.record.formula.functions;
 
 import org.apache.poi.hssf.record.formula.eval.AreaEval;
 import org.apache.poi.hssf.record.formula.eval.BlankEval;
-import org.apache.poi.hssf.record.formula.eval.ErrorEval;
 import org.apache.poi.hssf.record.formula.eval.NumberEval;
 import org.apache.poi.hssf.record.formula.eval.RefEval;
 import org.apache.poi.hssf.record.formula.eval.ValueEval;
@@ -36,17 +35,11 @@ import org.apache.poi.hssf.record.formula.functions.CountUtils.I_MatchPredicate;
  *
  * @author Mads Mohr Christensen
  */
-public final class Countblank implements Function {
+public final class Countblank extends Fixed1ArgFunction {
 
-	public ValueEval evaluate(ValueEval[] args, int srcRowIndex, int srcColumnIndex) {
-		if (args.length != 1) {
-			// TODO - it doesn't seem to be possible to enter COUNTBLANK() into Excel with the wrong arg count
-			// perhaps this should be an exception
-			return ErrorEval.VALUE_INVALID;
-		}
+	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0) {
 
 		double result;
-		ValueEval arg0 = args[0];
 		if (arg0 instanceof RefEval) {
 			result = CountUtils.countMatchingCell((RefEval) arg0, predicate);
 		} else if (arg0 instanceof AreaEval) {
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/Countif.java b/src/java/org/apache/poi/hssf/record/formula/functions/Countif.java
index 2b45debec9..77fdf9bfc7 100644
--- a/src/java/org/apache/poi/hssf/record/formula/functions/Countif.java
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/Countif.java
@@ -44,7 +44,7 @@ import org.apache.poi.ss.usermodel.ErrorConstants;
  *
  * @author Josh Micich
  */
-public final class Countif implements Function {
+public final class Countif extends Fixed2ArgFunction {
 
 	private static final class CmpOp {
 		public static final int NONE = 0;
@@ -400,23 +400,14 @@ public final class Countif implements Function {
 		}
 	}
 
-	public ValueEval evaluate(ValueEval[] args, int srcRowIndex, int srcColumnIndex) {
-		switch(args.length) {
-			case 2:
-				// expected
-				break;
-			default:
-				// TODO - it doesn't seem to be possible to enter COUNTIF() into Excel with the wrong arg count
-				// perhaps this should be an exception
-				return ErrorEval.VALUE_INVALID;
-		}
+	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0, ValueEval arg1) {
 
-		I_MatchPredicate mp = createCriteriaPredicate(args[1], srcRowIndex, srcColumnIndex);
+		I_MatchPredicate mp = createCriteriaPredicate(arg1, srcRowIndex, srcColumnIndex);
 		if(mp == null) {
 			// If the criteria arg is a reference to a blank cell, countif always returns zero.
 			return NumberEval.ZERO;
 		}
-		double result = countMatchingCellsInArea(args[0], mp);
+		double result = countMatchingCellsInArea(arg0, mp);
 		return new NumberEval(result);
 	}
 	/**
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/DateFunc.java b/src/java/org/apache/poi/hssf/record/formula/functions/DateFunc.java
index 8c06837168..ca6df7ae23 100644
--- a/src/java/org/apache/poi/hssf/record/formula/functions/DateFunc.java
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/DateFunc.java
@@ -22,23 +22,37 @@ import java.util.GregorianCalendar;
 
 import org.apache.poi.hssf.record.formula.eval.ErrorEval;
 import org.apache.poi.hssf.record.formula.eval.EvaluationException;
+import org.apache.poi.hssf.record.formula.eval.NumberEval;
+import org.apache.poi.hssf.record.formula.eval.ValueEval;
 import org.apache.poi.hssf.usermodel.HSSFDateUtil;
 
+
 /**
  * @author Pavel Krupets (pkrupets at palmtreebusiness dot com)
  */
-public final class DateFunc extends NumericFunction.MultiArg {
+public final class DateFunc extends Fixed3ArgFunction {
 
 	public static final Function instance = new DateFunc();
 
 	private DateFunc() {
-		super(3,3);
+		// no fields to initialise
+	}
+	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0, ValueEval arg1,
+			ValueEval arg2) {
+		double result;
+		try {
+			double d0 = NumericFunction.singleOperandEvaluate(arg0, srcRowIndex, srcColumnIndex);
+			double d1 = NumericFunction.singleOperandEvaluate(arg1, srcRowIndex, srcColumnIndex);
+			double d2 = NumericFunction.singleOperandEvaluate(arg2, srcRowIndex, srcColumnIndex);
+			result = evaluate(getYear(d0), (int) (d1 - 1), (int) d2);
+			NumericFunction.checkValue(result);
+		} catch (EvaluationException e) {
+			return e.getErrorEval();
+		}
+		return new NumberEval(result);
 	}
 
-	protected double evaluate(double[] ds) throws EvaluationException {
-		int year = getYear(ds[0]);
-		int month = (int) ds[1] - 1;
-		int day = (int) ds[2];
+	private static double evaluate(int year, int month, int day) throws EvaluationException {
 
 		if (year < 0 || month < 0 || day < 0) {
 			throw new EvaluationException(ErrorEval.VALUE_INVALID);
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/Errortype.java b/src/java/org/apache/poi/hssf/record/formula/functions/Errortype.java
index f96f3b2d8c..72de76273c 100644
--- a/src/java/org/apache/poi/hssf/record/formula/functions/Errortype.java
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/Errortype.java
@@ -50,12 +50,12 @@ import org.apache.poi.hssf.usermodel.HSSFErrorConstants;
  *
  * @author Josh Micich
  */
-public final class Errortype implements Function {
+public final class Errortype extends Fixed1ArgFunction {
 
-	public ValueEval evaluate(ValueEval[] args, int srcCellRow, int srcCellCol) {
+	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0) {
 
 		try {
-			OperandResolver.getSingleValue(args[0], srcCellRow, srcCellCol);
+			OperandResolver.getSingleValue(arg0, srcRowIndex, srcColumnIndex);
 			return ErrorEval.NA;
 		} catch (EvaluationException e) {
 			int result = translateErrorCodeToErrorTypeValue(e.getErrorEval().getErrorCode());
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/Fixed0ArgFunction.java b/src/java/org/apache/poi/hssf/record/formula/functions/Fixed0ArgFunction.java
new file mode 100644
index 0000000000..ff3207b319
--- /dev/null
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/Fixed0ArgFunction.java
@@ -0,0 +1,35 @@
+/* ====================================================================
+   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.hssf.record.formula.functions;
+
+import org.apache.poi.hssf.record.formula.eval.ErrorEval;
+import org.apache.poi.hssf.record.formula.eval.ValueEval;
+
+/**
+ * Convenience base class for functions that only take zero arguments.
+ *
+ * @author Josh Micich
+ */
+public abstract class Fixed0ArgFunction implements Function0Arg {
+	public final ValueEval evaluate(ValueEval[] args, int srcRowIndex, int srcColumnIndex) {
+		if (args.length != 0) {
+			return ErrorEval.VALUE_INVALID;
+		}
+		return evaluate(srcRowIndex, srcColumnIndex);
+	}
+}
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/Fixed1ArgFunction.java b/src/java/org/apache/poi/hssf/record/formula/functions/Fixed1ArgFunction.java
new file mode 100644
index 0000000000..6a12d9efc8
--- /dev/null
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/Fixed1ArgFunction.java
@@ -0,0 +1,35 @@
+/* ====================================================================
+   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.hssf.record.formula.functions;
+
+import org.apache.poi.hssf.record.formula.eval.ErrorEval;
+import org.apache.poi.hssf.record.formula.eval.ValueEval;
+
+/**
+ * Convenience base class for functions that must take exactly one argument.
+ *
+ * @author Josh Micich
+ */
+public abstract class Fixed1ArgFunction implements Function1Arg {
+	public final ValueEval evaluate(ValueEval[] args, int srcRowIndex, int srcColumnIndex) {
+		if (args.length != 1) {
+			return ErrorEval.VALUE_INVALID;
+		}
+		return evaluate(srcRowIndex, srcColumnIndex, args[0]);
+	}
+}
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/Fixed2ArgFunction.java b/src/java/org/apache/poi/hssf/record/formula/functions/Fixed2ArgFunction.java
new file mode 100644
index 0000000000..7695920b97
--- /dev/null
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/Fixed2ArgFunction.java
@@ -0,0 +1,35 @@
+/* ====================================================================
+   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.hssf.record.formula.functions;
+
+import org.apache.poi.hssf.record.formula.eval.ErrorEval;
+import org.apache.poi.hssf.record.formula.eval.ValueEval;
+
+/**
+ * Convenience base class for functions that must take exactly two arguments.
+ *
+ * @author Josh Micich
+ */
+public abstract class Fixed2ArgFunction implements Function2Arg {
+	public final ValueEval evaluate(ValueEval[] args, int srcRowIndex, int srcColumnIndex) {
+		if (args.length != 2) {
+			return ErrorEval.VALUE_INVALID;
+		}
+		return evaluate(srcRowIndex, srcColumnIndex, args[0], args[1]);
+	}
+}
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/Fixed3ArgFunction.java b/src/java/org/apache/poi/hssf/record/formula/functions/Fixed3ArgFunction.java
new file mode 100644
index 0000000000..d4488ab7b7
--- /dev/null
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/Fixed3ArgFunction.java
@@ -0,0 +1,35 @@
+/* ====================================================================
+   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.hssf.record.formula.functions;
+
+import org.apache.poi.hssf.record.formula.eval.ErrorEval;
+import org.apache.poi.hssf.record.formula.eval.ValueEval;
+
+/**
+ * Convenience base class for functions that must take exactly three arguments.
+ *
+ * @author Josh Micich
+ */
+public abstract class Fixed3ArgFunction implements Function3Arg {
+	public final ValueEval evaluate(ValueEval[] args, int srcRowIndex, int srcColumnIndex) {
+		if (args.length != 3) {
+			return ErrorEval.VALUE_INVALID;
+		}
+		return evaluate(srcRowIndex, srcColumnIndex, args[0], args[1], args[2]);
+	}
+}
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/Fixed4ArgFunction.java b/src/java/org/apache/poi/hssf/record/formula/functions/Fixed4ArgFunction.java
new file mode 100644
index 0000000000..5588714972
--- /dev/null
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/Fixed4ArgFunction.java
@@ -0,0 +1,35 @@
+/* ====================================================================
+   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.hssf.record.formula.functions;
+
+import org.apache.poi.hssf.record.formula.eval.ErrorEval;
+import org.apache.poi.hssf.record.formula.eval.ValueEval;
+
+/**
+ * Convenience base class for functions that must take exactly four arguments.
+ *
+ * @author Josh Micich
+ */
+public abstract class Fixed4ArgFunction implements Function4Arg {
+	public final ValueEval evaluate(ValueEval[] args, int srcRowIndex, int srcColumnIndex) {
+		if (args.length != 4) {
+			return ErrorEval.VALUE_INVALID;
+		}
+		return evaluate(srcRowIndex, srcColumnIndex, args[0], args[1], args[2], args[3]);
+	}
+}
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/Function0Arg.java b/src/java/org/apache/poi/hssf/record/formula/functions/Function0Arg.java
new file mode 100644
index 0000000000..c61a87e0a2
--- /dev/null
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/Function0Arg.java
@@ -0,0 +1,32 @@
+/* ====================================================================
+   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.hssf.record.formula.functions;
+
+import org.apache.poi.hssf.record.formula.eval.ValueEval;
+
+/**
+ * Implemented by all functions that can be called with zero arguments
+ *
+ * @author Josh Micich
+ */
+public interface Function0Arg extends Function {
+	/**
+	 * see {@link Function#evaluate(ValueEval[], int, int)}
+	 */
+	ValueEval evaluate(int srcRowIndex, int srcColumnIndex);
+}
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/Function1Arg.java b/src/java/org/apache/poi/hssf/record/formula/functions/Function1Arg.java
new file mode 100644
index 0000000000..42007fa4cc
--- /dev/null
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/Function1Arg.java
@@ -0,0 +1,32 @@
+/* ====================================================================
+   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.hssf.record.formula.functions;
+
+import org.apache.poi.hssf.record.formula.eval.ValueEval;
+
+/**
+ * Implemented by all functions that can be called with one argument
+ *
+ * @author Josh Micich
+ */
+public interface Function1Arg extends Function {
+	/**
+	 * see {@link Function#evaluate(ValueEval[], int, int)}
+	 */
+	ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0);
+}
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/Function2Arg.java b/src/java/org/apache/poi/hssf/record/formula/functions/Function2Arg.java
new file mode 100644
index 0000000000..b0ef472859
--- /dev/null
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/Function2Arg.java
@@ -0,0 +1,32 @@
+/* ====================================================================
+   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.hssf.record.formula.functions;
+
+import org.apache.poi.hssf.record.formula.eval.ValueEval;
+
+/**
+ * Implemented by all functions that can be called with two arguments
+ *
+ * @author Josh Micich
+ */
+public interface Function2Arg extends Function {
+	/**
+	 * see {@link Function#evaluate(ValueEval[], int, int)}
+	 */
+	ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0, ValueEval arg1);
+}
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/Function3Arg.java b/src/java/org/apache/poi/hssf/record/formula/functions/Function3Arg.java
new file mode 100644
index 0000000000..7ee32b81c2
--- /dev/null
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/Function3Arg.java
@@ -0,0 +1,32 @@
+/* ====================================================================
+   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.hssf.record.formula.functions;
+
+import org.apache.poi.hssf.record.formula.eval.ValueEval;
+
+/**
+ * Implemented by all functions that can be called with three arguments
+ *
+ * @author Josh Micich
+ */
+public interface Function3Arg extends Function {
+	/**
+	 * see {@link Function#evaluate(ValueEval[], int, int)}
+	 */
+	ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0, ValueEval arg1, ValueEval arg2);
+}
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/Function4Arg.java b/src/java/org/apache/poi/hssf/record/formula/functions/Function4Arg.java
new file mode 100644
index 0000000000..7089432f75
--- /dev/null
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/Function4Arg.java
@@ -0,0 +1,32 @@
+/* ====================================================================
+   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.hssf.record.formula.functions;
+
+import org.apache.poi.hssf.record.formula.eval.ValueEval;
+
+/**
+ * Implemented by all functions that can be called with four arguments
+ *
+ * @author Josh Micich
+ */
+public interface Function4Arg extends Function {
+	/**
+	 * see {@link Function#evaluate(ValueEval[], int, int)}
+	 */
+	ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0, ValueEval arg1, ValueEval arg2, ValueEval arg3);
+}
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/Na.java b/src/java/org/apache/poi/hssf/record/formula/functions/Na.java
index e1f9fa612a..c66080b9d5 100644
--- a/src/java/org/apache/poi/hssf/record/formula/functions/Na.java
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/Na.java
@@ -25,10 +25,9 @@ import org.apache.poi.hssf.record.formula.eval.ValueEval;
  *
  * @author Josh Micich
  */
-public final class Na implements Function {
+public final class Na extends Fixed0ArgFunction {
 
-	public ValueEval evaluate(ValueEval[] args, int srcCellRow, int srcCellCol) {
+	public ValueEval evaluate(int srcCellRow, int srcCellCol) {
 		return ErrorEval.NA;
 	}
-
 }
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/Now.java b/src/java/org/apache/poi/hssf/record/formula/functions/Now.java
index a56bf27052..766f5694d4 100644
--- a/src/java/org/apache/poi/hssf/record/formula/functions/Now.java
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/Now.java
@@ -19,7 +19,6 @@ package org.apache.poi.hssf.record.formula.functions;
 
 import java.util.Date;
 
-import org.apache.poi.hssf.record.formula.eval.ErrorEval;
 import org.apache.poi.hssf.record.formula.eval.NumberEval;
 import org.apache.poi.hssf.record.formula.eval.ValueEval;
 import org.apache.poi.hssf.usermodel.HSSFDateUtil;
@@ -29,13 +28,9 @@ import org.apache.poi.hssf.usermodel.HSSFDateUtil;
  *
  * @author Frank Taffelt
  */
-public final class Now implements Function {
-
-	public ValueEval evaluate(ValueEval[] evals, int srcCellRow, int srcCellCol) {
-		if (evals.length > 0) {
-			return ErrorEval.VALUE_INVALID;
-		}
+public final class Now extends Fixed0ArgFunction {
 
+	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex) {
 		Date now = new Date(System.currentTimeMillis());
 		return new NumberEval(HSSFDateUtil.getExcelDate(now));
 	}
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/NumericFunction.java b/src/java/org/apache/poi/hssf/record/formula/functions/NumericFunction.java
index 01ef88c3c6..24b0ae2692 100644
--- a/src/java/org/apache/poi/hssf/record/formula/functions/NumericFunction.java
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/NumericFunction.java
@@ -39,7 +39,10 @@ public abstract class NumericFunction implements Function {
 		return result;
 	}
 
-	private static final void checkValue(double result) throws EvaluationException {
+	/**
+	 * @throws EvaluationException (#NUM!) if <tt>result</tt> is <tt>NaN</> or <tt>Infinity</tt>
+	 */
+	static final void checkValue(double result) throws EvaluationException {
 		if (Double.isNaN(result) || Double.isInfinite(result)) {
 			throw new EvaluationException(ErrorEval.NUM_ERROR);
 		}
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/Replace.java b/src/java/org/apache/poi/hssf/record/formula/functions/Replace.java
index 2298656e7c..f2af838f91 100644
--- a/src/java/org/apache/poi/hssf/record/formula/functions/Replace.java
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/Replace.java
@@ -37,18 +37,23 @@ import org.apache.poi.hssf.record.formula.eval.ValueEval;
  *
  * @author Manda Wilson &lt; wilson at c bio dot msk cc dot org &gt;
  */
-public final class Replace extends TextFunction {
+public final class Replace extends Fixed4ArgFunction {
 
-	protected ValueEval evaluateFunc(ValueEval[] args, int srcCellRow, int srcCellCol)
-		throws EvaluationException {
-		if (args.length != 4) {
-			return ErrorEval.VALUE_INVALID;
-		}
+	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0, ValueEval arg1,
+			ValueEval arg2, ValueEval arg3) {
 
-		String oldStr = evaluateStringArg(args[0], srcCellRow, srcCellCol);
-		int startNum = evaluateIntArg(args[1], srcCellRow, srcCellCol);
-		int numChars = evaluateIntArg(args[2], srcCellRow, srcCellCol);
-		String newStr = evaluateStringArg(args[3], srcCellRow, srcCellCol);
+		String oldStr;
+		int startNum;
+		int numChars;
+		String newStr;
+		try {
+			oldStr = TextFunction.evaluateStringArg(arg0, srcRowIndex, srcColumnIndex);
+			startNum = TextFunction.evaluateIntArg(arg1, srcRowIndex, srcColumnIndex);
+			numChars = TextFunction.evaluateIntArg(arg2, srcRowIndex, srcColumnIndex);
+			newStr = TextFunction.evaluateStringArg(arg3, srcRowIndex, srcColumnIndex);
+		} catch (EvaluationException e) {
+			return e.getErrorEval();
+		}
 
 		if (startNum < 1 || numChars < 0) {
 			return ErrorEval.VALUE_INVALID;
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/Row.java b/src/java/org/apache/poi/hssf/record/formula/functions/Row.java
index d0d0acb2c5..718ab7c27a 100644
--- a/src/java/org/apache/poi/hssf/record/formula/functions/Row.java
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/Row.java
@@ -23,39 +23,33 @@ import org.apache.poi.hssf.record.formula.eval.NumberEval;
 import org.apache.poi.hssf.record.formula.eval.RefEval;
 import org.apache.poi.hssf.record.formula.eval.ValueEval;
 
-public final class Row implements Function {
-
-    public ValueEval evaluate(ValueEval[] evals, int srcCellRow, int srcCellCol) {
-        ValueEval retval = null;
-        int rnum = -1;
-
-        switch (evals.length) {
-        default:
-            retval = ErrorEval.VALUE_INVALID;
-        case 1:
-            if (evals[0] instanceof AreaEval) {
-                AreaEval ae = (AreaEval) evals[0];
-                rnum = ae.getFirstRow();
-            }
-            else if (evals[0] instanceof RefEval) {
-                RefEval re = (RefEval) evals[0];
-                rnum = re.getRow();
-            }
-            else { // anything else is not valid argument
-                retval = ErrorEval.VALUE_INVALID;
-            }
-            break;
-        case 0:
-            rnum = srcCellRow;
-        }
+public final class Row implements Function0Arg, Function1Arg {
 
-        if (retval == null) {
-            retval = (rnum >= 0)
-                    ? new NumberEval(rnum + 1) // +1 since excel rownums are 1 based
-                    : (ValueEval) ErrorEval.VALUE_INVALID;
+    public ValueEval evaluate(int srcRowIndex, int srcColumnIndex) {
+        return new NumberEval(srcRowIndex+1);
+    }
+    public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0) {
+        int rnum;
+
+        if (arg0 instanceof AreaEval) {
+            rnum = ((AreaEval) arg0).getFirstRow();
+        } else if (arg0 instanceof RefEval) {
+            rnum = ((RefEval) arg0).getRow();
+        } else {
+            // anything else is not valid argument
+            return ErrorEval.VALUE_INVALID;
         }
 
-        return retval;
+        return new NumberEval(rnum + 1);
+    }
+    public ValueEval evaluate(ValueEval[] args, int srcRowIndex, int srcColumnIndex) {
+        switch (args.length) {
+            case 1:
+                return evaluate(srcRowIndex, srcColumnIndex, args[0]);
+            case 0:
+              return new NumberEval(srcRowIndex+1);
+        }
+        return ErrorEval.VALUE_INVALID;
     }
 
 }
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/Rows.java b/src/java/org/apache/poi/hssf/record/formula/functions/Rows.java
index fb1b025342..dfde69ae31 100644
--- a/src/java/org/apache/poi/hssf/record/formula/functions/Rows.java
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/Rows.java
@@ -28,27 +28,14 @@ import org.apache.poi.hssf.record.formula.eval.ValueEval;
  *
  * @author Josh Micich
  */
-public final class Rows implements Function {
+public final class Rows extends Fixed1ArgFunction {
 
-	public ValueEval evaluate(ValueEval[] args, int srcCellRow, int srcCellCol) {
-		switch(args.length) {
-			case 1:
-				// expected
-				break;
-			case 0:
-				// too few arguments
-				return ErrorEval.VALUE_INVALID;
-			default:
-				// too many arguments
-				return ErrorEval.VALUE_INVALID;
-		}
-		ValueEval firstArg = args[0];
+	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0) {
 
 		int result;
-		if (firstArg instanceof AreaEval) {
-			AreaEval ae = (AreaEval) firstArg;
-			result = ae.getLastRow() - ae.getFirstRow() + 1;
-		} else if (firstArg instanceof RefEval) {
+		if (arg0 instanceof AreaEval) {
+			result = ((AreaEval) arg0).getHeight();
+		} else if (arg0 instanceof RefEval) {
 			result = 1;
 		} else { // anything else is not valid argument
 			return ErrorEval.VALUE_INVALID;
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/T.java b/src/java/org/apache/poi/hssf/record/formula/functions/T.java
index e4b43c0d1c..70869e462e 100644
--- a/src/java/org/apache/poi/hssf/record/formula/functions/T.java
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/T.java
@@ -30,16 +30,10 @@ import org.apache.poi.hssf.record.formula.eval.ValueEval;
  * cause an empty string result.  If the argument is an area, the first (top-left) cell is used
  * (regardless of the coordinates of the evaluating formula cell).
  */
-public final class T implements Function {
-
-    public ValueEval evaluate(ValueEval[] args, int srcCellRow, int srcCellCol) {
-        switch (args.length) {
-            default:
-                return ErrorEval.VALUE_INVALID;
-            case 1:
-                 break;
-        }
-        ValueEval arg = args[0];
+public final class T extends Fixed1ArgFunction {
+
+    public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0) {
+        ValueEval arg = arg0;
         if (arg instanceof RefEval) {
             arg = ((RefEval) arg).getInnerValueEval();
         } else if (arg instanceof AreaEval) {
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/Time.java b/src/java/org/apache/poi/hssf/record/formula/functions/Time.java
index 926ab3fed1..85f474028a 100644
--- a/src/java/org/apache/poi/hssf/record/formula/functions/Time.java
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/Time.java
@@ -29,7 +29,7 @@ import org.apache.poi.hssf.record.formula.eval.ValueEval;
  *
  * Based on POI org.apache.hssf.record.formula.DateFunc.java
  */
-public final class Time implements Function {
+public final class Time extends Fixed3ArgFunction {
 
 	private static final int SECONDS_PER_MINUTE = 60;
 	private static final int SECONDS_PER_HOUR = 3600;
@@ -37,25 +37,23 @@ public final class Time implements Function {
 	private static final int SECONDS_PER_DAY = HOURS_PER_DAY * SECONDS_PER_HOUR;
 
 
-	public ValueEval evaluate(ValueEval[] args, int srcCellRow, int srcCellCol) {
-		if (args.length != 3) {
-			return ErrorEval.VALUE_INVALID;
-		}
+	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0, ValueEval arg1,
+			ValueEval arg2) {
 		double result;
-
 		try {
-			result = evaluate(evalArg(args[0]), evalArg(args[1]), evalArg(args[2]));
+			result = evaluate(evalArg(arg0, srcRowIndex, srcColumnIndex), evalArg(arg1, srcRowIndex, srcColumnIndex), evalArg(arg2, srcRowIndex, srcColumnIndex));
 		} catch (EvaluationException e) {
 			return e.getErrorEval();
 		}
 		return new NumberEval(result);
 	}
-	private static int evalArg(ValueEval arg) throws EvaluationException {
+	private static int evalArg(ValueEval arg, int srcRowIndex, int srcColumnIndex) throws EvaluationException {
 		if (arg == MissingArgEval.instance) {
 			return 0;
 		}
+		ValueEval ev = OperandResolver.getSingleValue(arg, srcRowIndex, srcColumnIndex);
 		// Excel silently truncates double values to integers
-		return OperandResolver.coerceValueToInt(arg);
+		return OperandResolver.coerceValueToInt(ev);
 	}
 	/**
 	 * Converts the supplied hours, minutes and seconds to an Excel time value.
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/Today.java b/src/java/org/apache/poi/hssf/record/formula/functions/Today.java
index f6705aae10..f50ea73c1a 100644
--- a/src/java/org/apache/poi/hssf/record/formula/functions/Today.java
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/Today.java
@@ -20,7 +20,6 @@ package org.apache.poi.hssf.record.formula.functions;
 import java.util.Calendar;
 import java.util.GregorianCalendar;
 
-import org.apache.poi.hssf.record.formula.eval.ErrorEval;
 import org.apache.poi.hssf.record.formula.eval.NumberEval;
 import org.apache.poi.hssf.record.formula.eval.ValueEval;
 import org.apache.poi.hssf.usermodel.HSSFDateUtil;
@@ -30,12 +29,9 @@ import org.apache.poi.hssf.usermodel.HSSFDateUtil;
  *
  * @author Frank Taffelt
  */
-public final class Today implements Function {
+public final class Today extends Fixed0ArgFunction {
 
-	public ValueEval evaluate(ValueEval[] evals, int srcCellRow, int srcCellCol) {
-		if (evals.length > 0) {
-			return ErrorEval.VALUE_INVALID;
-		}
+	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex) {
 
 		Calendar now = new GregorianCalendar();
 		now.set(now.get(Calendar.YEAR), now.get(Calendar.MONTH), now.get(Calendar.DATE),0,0,0);
@@ -43,4 +39,3 @@ public final class Today implements Function {
 		return new NumberEval(HSSFDateUtil.getExcelDate(now.getTime()));
 	}
 }
-
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/Value.java b/src/java/org/apache/poi/hssf/record/formula/functions/Value.java
index 8067e742e6..951f19cb40 100644
--- a/src/java/org/apache/poi/hssf/record/formula/functions/Value.java
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/Value.java
@@ -35,19 +35,16 @@ import org.apache.poi.hssf.record.formula.eval.ValueEval;
  *
  * @author Josh Micich
  */
-public final class Value implements Function {
+public final class Value extends Fixed1ArgFunction {
 
 	/** "1,0000" is valid, "1,00" is not */
 	private static final int MIN_DISTANCE_BETWEEN_THOUSANDS_SEPARATOR = 4;
 	private static final Double ZERO = new Double(0.0);
 
-	public ValueEval evaluate(ValueEval[] args, int srcCellRow, int srcCellCol) {
-		if (args.length != 1) {
-			return ErrorEval.VALUE_INVALID;
-		}
+	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0) {
 		ValueEval veText;
 		try {
-			veText = OperandResolver.getSingleValue(args[0], srcCellRow, srcCellCol);
+			veText = OperandResolver.getSingleValue(arg0, srcRowIndex, srcColumnIndex);
 		} catch (EvaluationException e) {
 			return e.getErrorEval();
 		}
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/Var2or3ArgFunction.java b/src/java/org/apache/poi/hssf/record/formula/functions/Var2or3ArgFunction.java
index 9f5483fa05..4928425f99 100644
--- a/src/java/org/apache/poi/hssf/record/formula/functions/Var2or3ArgFunction.java
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/Var2or3ArgFunction.java
@@ -26,7 +26,7 @@ import org.apache.poi.hssf.record.formula.eval.ValueEval;
  *
  * @author Josh Micich
  */
-abstract class Var2or3ArgFunction implements Function {
+abstract class Var2or3ArgFunction implements Function2Arg, Function3Arg {
 
 	public final ValueEval evaluate(ValueEval[] args, int srcRowIndex, int srcColumnIndex) {
 		switch (args.length) {
@@ -37,10 +37,4 @@ abstract class Var2or3ArgFunction implements Function {
 		}
 		return ErrorEval.VALUE_INVALID;
 	}
-
-	public abstract ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0,
-			ValueEval arg1, ValueEval arg2);
-
-	public abstract ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0,
-			ValueEval arg1);
 }
diff --git a/src/java/org/apache/poi/hssf/record/formula/functions/XYNumericFunction.java b/src/java/org/apache/poi/hssf/record/formula/functions/XYNumericFunction.java
index 21c43d4855..e2c919489b 100644
--- a/src/java/org/apache/poi/hssf/record/formula/functions/XYNumericFunction.java
+++ b/src/java/org/apache/poi/hssf/record/formula/functions/XYNumericFunction.java
@@ -27,9 +27,8 @@ import org.apache.poi.hssf.record.formula.functions.LookupUtils.ValueVector;
 
 /**
  * @author Amol S. Deshmukh &lt; amolweb at ya hoo dot com &gt;
- *
  */
-public abstract class XYNumericFunction implements Function {
+public abstract class XYNumericFunction extends Fixed2ArgFunction {
 
 	private static abstract class ValueArray implements ValueVector {
 		private final int _size;
@@ -96,15 +95,12 @@ public abstract class XYNumericFunction implements Function {
 	 */
 	protected abstract Accumulator createAccumulator();
 
-	public final ValueEval evaluate(ValueEval[] args, int srcCellRow, int srcCellCol) {
-		if (args.length != 2) {
-			return ErrorEval.VALUE_INVALID;
-		}
+	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0, ValueEval arg1) {
 
 		double result;
 		try {
-			ValueVector vvX = createValueVector(args[0]);
-			ValueVector vvY = createValueVector(args[1]);
+			ValueVector vvX = createValueVector(arg0);
+			ValueVector vvY = createValueVector(arg1);
 			int size = vvX.getSize();
 			if (size == 0 || vvY.getSize() != size) {
 				return ErrorEval.NA;