When I compile the following,
#include <boost/numeric/ublas/vector.hpp>
#include <iomanip>
#include <stdio.h>
namespace ublas = boost::numeric::ublas;
template <class T> class Vector
{
private:
ublas::vector<T> m_ublas_vec;
unsigned m_size;
public:
Vector(unsigned s){
m_size = s;
m_ublas_vec.resize(m_size);
}
T &operator () (unsigned idx) {
if(idx >= m_size){
perror("ERROR: Index out of bounds!\n");
exit(1);
}
return m_ublas_vec(idx);
}
// Right-multiply by scalar.
template <class TT, class S>
friend Vector<TT> operator * (const Vector<TT> &, S);
// Left multiply by scalar.
template <class TT, class S>
friend Vector<TT> operator * (S, const Vector<TT> &);
};
template <class T, class S>
Vector<T> Vector<T>::operator * (const Vector<T> &v_in, S scalar){
Vector<T> v_out (v_in.m_size);
v_out.m_ublas_vec = v_in.m_ublas_vec*static_cast<T>(scalar);
return v_out;
}
template <class T, class S>
Vector<T> Vector<T>::operator * (S scalar, const Vector<T> &v_in){
Vector<T> v_out (v_in.m_size);
v_out.m_ublas_vec = v_in.m_ublas_vec*static_cast<T>(scalar);
return v_out;
}
I get this error:
vector_test.cpp:49:95: error: invalid use of incomplete type 'class Vector'
vector_test.cpp:7:26: error: declaration of 'class Vector'
What am I doing wrong?
You friend
functions don't declare member functions. So, you want to define them as
template <class T, class S>
Vector<T> operator * (const Vector<T> &v_in, S scalar){
Vector<T> v_out (v_in.m_size);
v_out.m_ublas_vec = v_in.m_ublas_vec*static_cast<T>(scalar);
return v_out;
}
template <class T, class S>
Vector<T> operator * (S scalar, const Vector<T> &v_in){
Vector<T> v_out (v_in.m_size);
v_out.m_ublas_vec = v_in.m_ublas_vec*static_cast<T>(scalar);
return v_out;
}
friend
function is not a part of class. You should not define it via Vector<T>::
specifier. Correct one is:
template <class T, class S>
Vector<T> operator * (const Vector<T> &v_in, S scalar){
Vector<T> v_out (v_in.m_size);
v_out.m_ublas_vec = v_in.m_ublas_vec*static_cast<T>(scalar);
return v_out;
}
template <class T, class S>
Vector<T> operator * (S scalar, const Vector<T> &v_in){
Vector<T> v_out (v_in.m_size);
v_out.m_ublas_vec = v_in.m_ublas_vec*static_cast<T>(scalar);
return v_out;
}
Check: http://ideone.com/8n9UO1
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