Quote:Original post by the_edd

Quote:Original post by johnstanp
I had problems understanding the traits mechanism which I thought was related to type information...

It usually is used for that, but that's not the heart of the concept. Traits allow you to use 3rd party code with yours without changing the 3rd party implementation. Concept maps in the next revision of the standard takes this idea even further.

The other plus of this is that you don't need to add an extra warty template parameter to your vector class.

Quote:Original post by johnstanp

Quote:Original post by the_edd

Quote:Original post by johnstanp
I had problems understanding the traits mechanism which I thought was related to type information...

It usually is used for that, but that's not the heart of the concept. Traits allow you to use 3rd party code with yours without changing the 3rd party implementation. Concept maps in the next revision of the standard takes this idea even further.

The other plus of this is that you don't need to add an extra warty template parameter to your vector class.

I didn't pay close attention to the mechanism you provided. Actually, depending of the type parameter of my vector class, a template specialization would be chosen: so I won't need passing a pointer. The problem is that I want too, to be able to use std::sqrt() which gives better results thant my sqrt algorithm. As the std::sqrt() uses the same types as my function, if I am not mistaken, I won't be able to use that mechanism.

template <class T>class Vector3{public:	T x, y, z;	// generic empty method	T length (void) { return T(); }};// integer square root functionint iSqrt (int x){	/* calculate integer sqrt */	return x;}// implementation for Vector3 <int>template <> int Vector3 <int>::length (void){	return iSqrt (x * x + y * y + z * z);}// implementation for Vector3 <float>template <> float Vector3 <float>::length (void){	return std::sqrt (x * x + y * y + z * z);}

Quote:Original post by johnstanp

Quote:Original post by lexs
If i understand you correctly you want something like this:


*** Source Snippet Removed ***

That's it!

template<typename T>class Vector3{	public:		...                template<typename Math>		T length() const		{                        return Math::sqrt(...);		}			private:		T x_[3];};class StdMath{public:	static float sqrt(float x)	{		return std::sqrt(x);	}};Vector<float> Vector;float v = Vector::length<StdMath>();

Quote:Original post by Moomin

A template function seems more flexible :

*** Source Snippet Removed ***

Quote:Original post by johnstanp

Quote:Original post by Moomin

A template function seems more flexible :

*** Source Snippet Removed ***

Thank you very much Moomin!!!
That's exactly what I wanted.

Thank you guys for your precious help!!!

PS:well, thre3dee, I can specialize member functions of a template class?
It seems that GCC doesn't allow it, or have I done something incorrectly?

Quote:Original post by thre3dee
I haven't used GCC but I assumed template specialisation was part of standard C++; amirong?

Quote:Original post by johnstanp

Quote:Original post by thre3dee
I haven't used GCC but I assumed template specialisation was part of standard C++; amirong?

Actually, I cannot specialize a member function of a class template without specializing the whole class. I've got various compile errors, that informs me that all member variables have incomplete types.