Re: template function member with const classifier

From:
"Victor Bazarov" <v.Abazarov@comAcast.net>
Newsgroups:
comp.lang.c++
Date:
Wed, 14 Jun 2006 09:27:39 -0400
Message-ID:
<e6p2sd$sqr$1@news.datemas.de>
Pedro Sousa wrote:

I'm trying to create an template class that represent points in all
possible dimensions, what I've made until now is

#ifndef _POINT_HPP_
#define _POINT_HPP_


Names beginning with an underscore and a capital letter are reserved
by the implemenation. IOW, you can't use them. Why do you think you
need the leading underscore, anyway?

#include <vector>

template <typename T>
class Point{
private:
  std::vector<T> coordinates;

public:
  explicit Point( int n );

  Point( const Point<T>& other );

  Point( const std::vector<T>& coord );

  ~Point();

  std::vector<T> Get_Coordinates() const;

  void Set_Coordinates( const std::vector<T>& coord );

  void Translate( const std::vector<T>& coord );

  void Scale( const T& factor );

  //unsigned int Distance( const Point<T>& other );

  //unsigned int Distance_Origin()

  void WriteLn();

private:
  static const int Expt_Different_Sizes;

};

template <typename T>
Point<T>::Point( int n ):
  coordinates( n )
{
}

template <typename T>
Point<T>::Point( const Point<T>& other ):
  coordinates( other.coordinates )
{
}

template <typename T>
Point<T>::Point( const std::vector<T>& coord ):
  coordinates( coord )
{
}

template <typename T>
Point<T>::~Point()
{
}

template <typename T>
void Point<T>::Set_Coordinates( const std::vector<T>& coord )
{
  if( coordinates.size() != coord.size() )
    throw Point<T>::Expt_Different_Sizes;
  else
    {
for( int i=0; i<coordinates.size(); i++ )
   coordinates[i] = coord[i];
    }
}

template <typename T>
std::vector<T> Get_Coordinates() const

               ^^^^
Name of the class is missing here. At least that's what your
compiler is telling you.

{
  return coordinates;
}

[...]
#endif

But I'm getting the errors

In file included from src/GUI.cpp:12:
include/point.hpp:84: error: non-member function `std::vector<T,
   std::allocator<_CharT> > Get_Coordinates()' cannot have `const'
   method qualifier


You need to supply the name of the class for which you are defining
the member.

[..]
template <typename T>
void Point<T>::Translate( const std::vector<T>& coord )
{
  if( coordinates.size() != coord.size() )
    throw Point<T>::Expt_Different_Sizes;

  // Add the two coordinates
  for( int i = 0; i < coordinates.size(); ++i )
    coordinates[i] = coordinates[i] + coord[i];
}

template <typename T>
void Point<T>::Scale( const T& factor )
{
  if( factor == 0 )
    throw Point<T>::Expt_Divide_By_Zero;
  else
    {
for( int i = 0; i< coordinates.size(); i++ )
   coordinates[i] = coordinates[i]/factor;
    }
}

template <typename T>
void Point<T>::WriteLn()
{
  typename std::vector<T>::iterator pos;

  for( pos = coordinates.begin(); pos < coordinates.end(); ++pos)
    std::cout << *pos << " ";

  std::cout << std::endl;
}

// Specify the exception code
template <typename T>
const int Point<T>::Expt_Different_Sizes = 1;

template <typename T>
const int Point<T>::Expt_Divide_By_Zero = 2;


I don't think you declared that member in the class. Look at the
class template definition.

#endif
 nt<T>::Expt_Different_Sizes;


Huh? Is this just a typo? Please have a closer look at what you
give to your compiler. You know, GIGO...

  // Add the two coordinates
  for( int i = 0; i < coordinates.size(); ++i )
    coordinates[i] = coordinates[i] + coord[i];
}

[..]

include/point.hpp:127: error: `const int
Point<T>::Expt_Divide_By_Zero' is not
   a static member of `class Point<T>'
include/point.hpp:127: error: template definition of non-template
`const int
   Point<T>::Expt_Divide_By_Zero'
make: *** [GUI.o] Error 1

Can any one give me an inch about want I'm doing wrong? If you could
send me some links I would appreciate.


What links? Just clean up your code, buddy.

V
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