15. Default template arguments

• Templates arguments can default.

• As with function arguments, this is like overloading:

  
  template < typename Type1, typename Type2 = double >
  class Point {
  public:
      // Constructor
      Point< Type1, Type2 >( Type1 x, Type2 y)
          : m_x( x ), m_y( y )
      {
      }
  
      Type2 distance()
      {
          return static_cast< Type2 >( sqrt( m_x * m_x + m_y * m_y ) );
      }
  
  private:
      Type1 m_x;
      Type2 m_y;
  
  };//class Point