template class: ctor against function -> new C++ standard
- by Oops
Hi
in this question:
http://stackoverflow.com/questions/2779155/template-point2-double-point3-double
Dennis and Michael noticed the unreasonable foolishly implemented constructor.
They were right, I didn't consider this at that moment.
But I found out that a constructor does not help very much for a template class like this one, instead a function is here much more convenient and safe
namespace point {
template < unsigned int dims, typename T >
struct Point {
T X[ dims ];
std::string str() {
std::stringstream s;
s << "{";
for ( int i = 0; i < dims; ++i ) {
s << " X" << i << ": " << X[ i ] << (( i < dims -1 )? " |": " ");
}
s << "}";
return s.str();
}
Point<dims, int> toint() {
Point<dims, int> ret;
std::copy( X, X+dims, ret.X );
return ret;
}
};
template < typename T >
Point< 2, T > Create( T X0, T X1 ) {
Point< 2, T > ret;
ret.X[ 0 ] = X0; ret.X[ 1 ] = X1;
return ret;
}
template < typename T >
Point< 3, T > Create( T X0, T X1, T X2 ) {
Point< 3, T > ret;
ret.X[ 0 ] = X0; ret.X[ 1 ] = X1; ret.X[ 2 ] = X2;
return ret;
}
template < typename T >
Point< 4, T > Create( T X0, T X1, T X2, T X3 ) {
Point< 4, T > ret;
ret.X[ 0 ] = X0; ret.X[ 1 ] = X1; ret.X[ 2 ] = X2; ret.X[ 3 ] = X3;
return ret;
}
};
int main( void ) {
using namespace point;
Point< 2, double > p2d = point::Create( 12.3, 34.5 );
Point< 3, double > p3d = point::Create( 12.3, 34.5, 56.7 );
Point< 4, double > p4d = point::Create( 12.3, 34.5, 56.7, 78.9 );
//Point< 3, double > p1d = point::Create( 12.3, 34.5 ); //no suitable user defined conversion exists
//Point< 3, int > p1i = p4d.toint(); //no suitable user defined conversion exists
Point< 2, int > p2i = p2d.toint();
Point< 3, int > p3i = p3d.toint();
Point< 4, int > p4i = p4d.toint();
std::cout << p2d.str() << std::endl;
std::cout << p3d.str() << std::endl;
std::cout << p4d.str() << std::endl;
std::cout << p2i.str() << std::endl;
std::cout << p3i.str() << std::endl;
std::cout << p4i.str() << std::endl;
char c;
std::cin >> c;
}
has the new C++ standard any new improvements, language features or simplifications regarding this aspect of ctor of a template class?
what do you think about the implementation of the combination of namespace, stuct and Create function?
many thanks in advance
Oops
