Implement Cell function

main/SS/Formula/Eval/FunctionEval.cs

@@ -221,7 +221,7 @@ private static Function[] ProduceFunctions()
             retval[122] = new NotImplementedFunction("NAMES"); // NAMES
             retval[123] = new NotImplementedFunction("DIRECTORY"); // DIRECTORY
             retval[124] = TextFunction.FIND; // Find
-            retval[125] = new NotImplementedFunction("CELL"); // CELL
+            retval[125] = new Cell(); // CELL
             retval[126] = LogicalFunction.ISERR; // IsERR
             retval[127] = LogicalFunction.ISTEXT; // IsTEXT
             retval[128] = LogicalFunction.ISNUMBER; // IsNUMBER

main/SS/Formula/Functions/Cell.cs

@@ -0,0 +1,77 @@
+/*
+2020-03-20 Buzz Weetman
+Custom created because NPOI doesn't implement CELL.
+I am specifically fixing a case where it is used as CELL("col",W2)
+The COLUMN function will do that same thing as COLUMN(W2)
+But to avoid having to change existing templates, this implementation has been made.
+It only handles the "col" and "row" parameters.
+ */
+namespace NPOI.SS.Formula.Functions
+{
+    using NPOI.SS.Formula.Eval;
+
+    public class Cell : Function2Arg
+    {
+        public ValueEval Evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0, ValueEval arg1)
+        {
+            string s0 = TextFunction.EvaluateStringArg(arg0, srcRowIndex, srcColumnIndex);
+
+            // Only "col" and "row" are implemented
+
+            int rnum;
+
+            if(string.Equals(s0, "col", System.StringComparison.InvariantCultureIgnoreCase))
+            {
+                // "col"
+                if(arg1 is AreaEval)
+                {
+                    rnum = ((AreaEval) arg1).FirstColumn;
+                }
+                else if(arg1 is RefEval)
+                {
+                    rnum = ((RefEval) arg1).Column;
+                }
+                else
+                {
+                    // anything else is not valid argument
+                    return ErrorEval.VALUE_INVALID;
+                }
+            }
+            else if(string.Equals(s0, "row", System.StringComparison.InvariantCultureIgnoreCase))
+            {
+                // "row"
+                if(arg1 is AreaEval)
+                {
+                    rnum = ((AreaEval) arg1).FirstRow;
+                }
+                else if(arg1 is RefEval)
+                {
+                    rnum = ((RefEval) arg1).Row;
+                }
+                else
+                {
+                    // anything else is not valid argument
+                    return ErrorEval.VALUE_INVALID;
+                }
+            }
+            else
+            {
+                //https://support.microsoft.com/en-us/office/cell-function-51bd39a5-f338-4dbe-a33f-955d67c2b2cf
+                // anything else is not valid argument, until we implement more
+                return ErrorEval.VALUE_INVALID;
+            }
+
+            return new NumberEval(rnum + 1);
+        }
+
+        public ValueEval Evaluate(ValueEval[] args, int srcRowIndex, int srcColumnIndex)
+        {
+            if (args.Length == 2)
+            {
+                return Evaluate(srcRowIndex, srcColumnIndex, args[0], args[1]);
+            }
+
+            return ErrorEval.VALUE_INVALID;
+        }
+    }
+}

testcases/main/SS/Formula/Functions/TestRowCol.cs

@@ -47,6 +47,21 @@ public void TestCol()
             }
         }
         [Test]
+        public void TestCell()
+        {
+            Function target = new Cell();
+            {
+                ValueEval[] args = { new StringEval("col"), EvalFactory.CreateRefEval("B5"), };
+                double actual = NumericFunctionInvoker.Invoke(target, args);
+                Assert.AreEqual(2, actual);
+            }
+            {
+                ValueEval[] args = { new StringEval("row"), EvalFactory.CreateRefEval("B5"), };
+                double actual = NumericFunctionInvoker.Invoke(target, args);
+                Assert.AreEqual(5, actual);
+            }
+        }
+        [Test]
         public void TestRow()
         {
             //throw new NotImplementedException();