Problem on template definition

[shuisheng]

Dear All;

Would you please help me to look at the following case:

//! Rotation.
enum Rotation {
NON_CYCLIC,
CYCLIC
};
//! Rotation.
enum Direction {
LEFT,
RIGHT
};

//! This is a class template of TinyVector
template<class _T, size_t _n>
class TinyVector
{
public:
//! Rotate.
template<Direct ion _dir, Rotation _rot>
TinyVector& Rotate(size_t n);
}

//! Rotate.
template<class _T, size_t _n>
template<Direct ion _dir, Rotation _rot>
inline typename TinyVector<_T, _n>& TinyVector<_T, _n>::Rotate(siz e_t
n)
{
...
return *this;
}

//! Rotate<LEFT, NON_CYCLIC>.
template<class _T, size_t _n>
template<>
inline typename TinyVector<_T, _n>& TinyVector<_T, _n>::Rotate<LEF T,
NON_CYCLIC>(siz e_t n)
{
...
return *this;
} // <-- Error position

Error C2768: 'TinyVector<_T, _n>::Rotate' : illegal use of explicit
template arguments

I realy appreciate your guys' help. It make me to learn c++ much more
comforably.

Shuisheng

[shuisheng]

Re: Problem on template definition


shuisheng wrote:

Dear All;
>
Would you please help me to look at the following case:
>
//! Rotation.
enum Rotation {
NON_CYCLIC,
CYCLIC
};
//! Rotation.
enum Direction {
LEFT,
RIGHT
};
>
//! This is a class template of TinyVector
template<class _T, size_t _n>
class TinyVector
{
public:
//! Rotate.
template<Direct ion _dir, Rotation _rot>
TinyVector& Rotate(size_t n);
}
>
//! Rotate.
template<class _T, size_t _n>
template<Direct ion _dir, Rotation _rot>
inline typename TinyVector<_T, _n>& TinyVector<_T, _n>::Rotate(siz e_t
n)
{
...
return *this;
}
>
//! Rotate<LEFT, NON_CYCLIC>.
template<class _T, size_t _n>
template<>

Reverse those two template declaration. It becomes okay. Quite
interesting.

template<>
template<class _T, size_t _n>

inline typename TinyVector<_T, _n>& TinyVector<_T, _n>::Rotate<LEF T,
NON_CYCLIC>(siz e_t n)
{
...
return *this;
} // <-- Error position
>
Error C2768: 'TinyVector<_T, _n>::Rotate' : illegal use of explicit
template arguments
>
I realy appreciate your guys' help. It make me to learn c++ much more
comforably.
>
Shuisheng

[shuisheng]

Re: Problem on template definition


shuisheng wrote:

shuisheng wrote:

Dear All;

Would you please help me to look at the following case:

//! Rotation.
enum Rotation {
NON_CYCLIC,
CYCLIC
};
//! Rotation.
enum Direction {
LEFT,
RIGHT
};

//! This is a class template of TinyVector
template<class _T, size_t _n>
class TinyVector
{
public:
//! Rotate.
template<Direct ion _dir, Rotation _rot>
TinyVector& Rotate(size_t n);
}

//! Rotate.
template<class _T, size_t _n>
template<Direct ion _dir, Rotation _rot>
inline typename TinyVector<_T, _n>& TinyVector<_T, _n>::Rotate(siz e_t
n)
{
...
return *this;
}

//! Rotate<LEFT, NON_CYCLIC>.
template<class _T, size_t _n>
template<>

>
Reverse those two template declaration. It becomes okay. Quite
interesting.
>
template<>
template<class _T, size_t _n>
>
>

inline typename TinyVector<_T, _n>& TinyVector<_T, _n>::Rotate<LEF T,
NON_CYCLIC>(siz e_t n)
{
...
return *this;
} // <-- Error position

Error C2768: 'TinyVector<_T, _n>::Rotate' : illegal use of explicit
template arguments

I realy appreciate your guys' help. It make me to learn c++ much more
comforably.

Shuisheng

Still WRONG. Help!!!

[amparikh@gmail.com]

Re: Problem on template definition


shuisheng wrote:

Dear All;
>
Would you please help me to look at the following case:
>
//! Rotation.
enum Rotation {
NON_CYCLIC,
CYCLIC
};
//! Rotation.
enum Direction {
LEFT,
RIGHT
};
>
//! This is a class template of TinyVector
template<class _T, size_t _n>
class TinyVector
{
public:
//! Rotate.
template<Direct ion _dir, Rotation _rot>
TinyVector& Rotate(size_t n);
}
>
//! Rotate.
template<class _T, size_t _n>
template<Direct ion _dir, Rotation _rot>
inline typename TinyVector<_T, _n>& TinyVector<_T, _n>::Rotate(siz e_t
n)
{
...
return *this;
}
>
//! Rotate<LEFT, NON_CYCLIC>.
template<class _T, size_t _n>
template<>
inline typename TinyVector<_T, _n>& TinyVector<_T, _n>::Rotate<LEF T,
NON_CYCLIC>(siz e_t n)
{
...
return *this;
} // <-- Error position

You cannot specialize a template member function without first
specializing the class template.
so you need to first specialize the class template for a specific type.

>
Error C2768: 'TinyVector<_T, _n>::Rotate' : illegal use of explicit
template arguments
>
I realy appreciate your guys' help. It make me to learn c++ much more
comforably.
>
Shuisheng

[Kai-Uwe Bux]

Re: Problem on template definition

shuisheng wrote:

//! Rotation.
enum Rotation           {
NON_CYCLIC,
CYCLIC
};
//! Rotation.
enum Direction          {
LEFT,
RIGHT
};
>
//! This is a class template of TinyVector
template<class _T, size_t _n>
class TinyVector
{
public:
//! Rotate.
template<Direct ion _dir, Rotation _rot>
TinyVector& Rotate(size_t n);
}

missing ";":
};

that one already causes a lot of confusing error messages to go away.

>
//! Rotate.
template<class _T, size_t _n>
template<Direct ion _dir, Rotation _rot>
inline typename TinyVector<_T, _n>& TinyVector<_T, _n>::Rotate(siz e_t n)

ditch the "typename"

{
...
return *this;
}
>
//! Rotate<LEFT, NON_CYCLIC>.
template<class _T, size_t _n>
template<>
inline typename TinyVector<_T, _n>& TinyVector<_T, _n>::Rotate<LEF T,
NON_CYCLIC>(siz e_t n)
{
...
return *this;
}   // <-- Error position
>

Finally, this last one cannot fly at all: as of the current standard,
partial specializations of function templates do not exist in C++. You have
to turn that into a class template. The class could be stateless and just
provide a static function.


You could try something like:

#include <cstddef>

typedef int Direction;
typedef int Rotation;

//! This is a class template of TinyVector
template<class T, size_t N >
class TinyVector;

template < Direction dir, Rotation rot >
struct alg;

template<>
struct alg< 0, 0 {

template<class T, size_t N >
static
TinyVector<T,N& rotate ( TinyVector<T,N& arg ) {
return ( arg );
}

}; // alg;


template<class T, size_t N >
class TinyVector {

public:

template<Direct ion dir, Rotation rot>
TinyVector& Rotate(size_t n) {
return ( alg<dir,rot>::r otate( *this ) );
}

};




Best

Kai-Uwe Bux

[Nate Barney]

Re: Problem on template definition

shuisheng wrote:

template<class _T, size_t _n>

Identifiers which begin with an underscore are reserved for the
implementation. Use T and n instead. If you really want to use an
underscore, you can use T_ and n_ .

Nate

[Victor Bazarov]

Re: Problem on template definition

Nate Barney wrote:

shuisheng wrote:

>template<cla ss _T, size_t _n>

>
Identifiers which begin with an underscore are reserved for the
implementation.

Only in the global scope. Of course those that begin with a '_'
and a capital letter (like "_T" here) are always reserved, no
matter what scope.

Use T and n instead. If you really want to use an
underscore, you can use T_ and n_ .

I think many who use the leading underscore think that with it
their code looks cool because it looks more like the "internal
stuff" or the "implementa tion detail", or some such. Or, maybe
they think it would help avoid naming conflict somewhere down
the road (which it actually doesn't).

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

[Nate Barney]

Re: Problem on template definition

Victor Bazarov wrote:

Nate Barney wrote:

>Identifiers which begin with an underscore are reserved for the
>implementation .

>
Only in the global scope. Of course those that begin with a '_'
and a capital letter (like "_T" here) are always reserved, no
matter what scope.

Interesting, I didn't know that. In any case, it's probably best to
eschew leading underscores entirely.

Nate