Rational numbers

A rational number can be expressed as a fraction of two integers, called the numerator and denominator.

Rational.h

namespace SmallWindows { 
  class NotaRationalNumber : public exception { 
    public: 
      NotaRationalNumber() {/* Empty. */} 
  }; 

The default constructor initializes the numerator and denominator to 0 and 1, respectively. The second constructor takes a string and throws a NotaRationalNumber exception if the string does not hold a valid rational number. The copy constructor and the assignment operator take another rational number. The String conversion operator returns the rational number as a string:

  class Rational { 
    public: 
      Rational(int numerator = 0, int denominator = 1); 
      Rational(const String& text); 
      Rational(const Rational &rational); 
      Rational operator=(const Rational &complex); 
      operator String() const; 
      bool operator==(const Rational &rational) const; 
      bool operator!=(const Rational...