Error C2555 with pointer to class with no template instantiation?

Error C2555
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c:\C++ projects\stat1\stdmatrix_adapt.h(41) : error C2555:
'std_tools::Matrix_adapter<T>::at': overriding virtual function return
type differs and is not covariant from 'ple::imtx_impl<T>::at'
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//in my program: the derived class
template <class T>
class Matrix_adapter : public ple::imtx_impl<T{
protected:
Matrix* m_;
public:
virtual const T& at(mtx_size i0, mtx_size i1) const //mtx_size -->
unsigned int
{return m_->at(i0, i1);}
}
// the base class
template <class T>
class imtx_impl : public imtx<T{
virtual const T& at(mtx_size i0, mtx_size i1) const=0;
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/*Notice Matrix_adapter.at returns a pointer to another class Matrix
m_
The problem arises as this class Matrix has no template instantiation
and i set the virtual function at return as double, the same as T */
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class Matrix : public GeneralMatrix
public:{
const double& at(unsigned int pos0, unsigned int pos1) const { return
v_.at(c_(pos0, pos1)); }
}
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// However in my main program initiating T as double in the derived
class still gives the error C2555.
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Matrix_adapter <doublematx;
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Am at loss what to do now.. any people care to help... ?
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erictham...@gmail.com wrote:>>>>>>>>
The code fragments as posted look OK, can you reproduce the problem with
a self contained example?
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--
Ian Collins.- Hide quoted text -
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- Show quoted text -

On Mar 5, 1:50 pm, Ian Collins <ian-n...@hotmail.comwrote:>
Ya i thought the derived and base classes look ok. Except that the
class that the pointer points is not a template class.