private Cell ParseSingleOperandFormula(int rowIndex, int columnIndex, FormulaStrategy strategy)
        {
            var cell     = CreateEmptyCell(rowIndex, columnIndex);
            var argument = ParseReferenceCell();

            strategy.Cells.Add(argument);
            cell.Formula   = strategy;
            cell.ValueType = strategy.ResultValueType;

            return(cell);
        }
        private Cell ParseMultiOperandFormula(int rowIndex, int columnIndex, FormulaStrategy strategy)
        {
            var cell      = CreateEmptyCell(rowIndex, columnIndex);
            var arguments = ParseArrayOfCells();

            strategy.Cells = arguments;
            cell.Formula   = strategy;
            cell.ValueType = strategy.ResultValueType;

            return(cell);
        }