             
             if unicodeInt == kDecimalPoint
             {
-                if self.text.contains(kDot)
+                if textView.text.contains(kDot)
                 {
                     return false
                 }

    
    func textViewDidChange(_ textView:UITextView)
    {
        if text.characters.count == 2
        {
            let firstCharacter:Character = text[text.startIndex]

    
    //MARK: private
    
    private func asDecimal()
    {
        self.viewText?.removeFromSuperview()
        self.viewDivision?.removeFromSuperview()
        
        let viewText:VLinearEquationsPolynomialText = VLinearEquationsPolynomialText(
            controller:self.controller)
        self.viewText = viewText
        
        addSubview(viewText)
        
        NSLayoutConstraint.equals(
            view:viewText,
            toView:self)
    }
    
    private func asDivision()
    {
        self.viewText?.removeFromSuperview()
        self.viewDivision?.removeFromSuperview()
        
        let viewDivision:VLinearEquationsPolynomialDivision = VLinearEquationsPolynomialDivision(
            controller:self.controller)
        self.viewDivision = viewDivision
        
        addSubview(viewDivision)
        
        NSLayoutConstraint.equals(
            view:viewDivision,
            toView:self)
    }
    
    private func curatedNumber(number:String) -> String
    {
        let curatedString:String = number.replacingOccurrences(
            of:kComma,
            with:kEmpty)
        
        return curatedString
    }
    
    private func textToPolynomial()
    {
        guard
            
            let polynomial:DPolynomial = controller.polynomial
            
        else
        {
            return
        }
        
        if polynomial.showAsDivision
        {
            guard
            
                let textDividend:String = viewDivision?.fieldDividend.text,
                let textDivisor:String = viewDivision?.fieldDivisor.text,
                let numberDividend:NSNumber = numberFormatter.number(
                    from:textDividend),
                let numberDivisor:NSNumber = numberFormatter.number(
                    from:textDivisor)
            
            else
            {
                return
            }
            
            let dividendDouble:Double = numberDividend as Double
            let divisorDouble:Double = numberDivisor as Double
            polynomial.coefficientDividend = dividendDouble
            polynomial.coefficientDivisor = divisorDouble
            
        }
        else
        {
            guard
                
                let text:String = viewText?.text,
                let number:NSNumber = numberFormatter.number(
                    from:text)
                
            else
            {
                return
            }
            
            let numberDouble:Double = number as Double
            polynomial.coefficientDividend = numberDouble
            polynomial.coefficientDivisor = 1
        }
    }
    
    private func readPolynomial()
