Hello everyone,
After I could not overload the << operator as a friend operator in my
template class (yes, it did not have to be a template class, but I was
testing something for the class I was going to teach) , I declared the
operator outside the class definition. This would prevent the operator
from accessing the private elements within the class, so I provided
access to elements of the private vector array thru a public member
function. But then I found that I could not place the const specifier
before the templated class argument in the overloaded operator
definition:
template <class C> ostream& operator << (ostream& os, const
Polynom<C>& p)
{
for(int i=p.GetOrder()+ 1; i>0; i--)
{
os << p.Coeff(i) << "*x^" << i << " + ";
}
os << p.Coeff(0) << endl;
return os;
}
The compiler (Bloodshed Dev C++) complained that passing a Polynom<int>
or a Polynom<double> instance to the operator would discard qualifiers.
I suppose the compiler wants the array member returned by the
Coeff(int) member function to be const as well, but I could not add the
const specifier in that definition. It did not supress the error
message.
Can anybody see what I am doing wrong?
Relevant code follows:
in the .hpp file:
template <class C> class Polynom
{
/*** Constructors and Destructors ***/
...
/*** Public methods ***/
...
C Coeff(int i);
...
/*** Data members ***/
private:
vector<C> coef;
};
in the .cpp file:
template <class C> C Polynom <C>::Coeff(in t i)
{
return coef[i];
}
My regards,
Hurol Aslan 4 3218
gobis wrote: template <class C> ostream& operator << (ostream& os, const Polynom<C>& p) { for(int i=p.GetOrder()+ 1; i>0; i--) { os << p.Coeff(i) << "*x^" << i << " + "; } os << p.Coeff(0) << endl; return os; }
in the .hpp file:
template <class C> class Polynom { /*** Constructors and Destructors ***/ ... /*** Public methods ***/ ... C Coeff(int i); ... /*** Data members ***/ private: vector<C> coef; };
in the .cpp file:
template <class C> C Polynom <C>::Coeff(in t i) { return coef[i]; }
Two issues: Coeff can't change this->coef, so it should be const
(so it can be called on a Polynom const&) and your compiler doesn't
have the keyword 'export' which you need to put a template definition
in a .cpp file.
HTH,
Michiel Salters Mi************* @tomtom.com wrote: your compiler doesn't have the keyword 'export' which you need to put a template definition in a .cpp file.
That's a bit disingenuous. See the FAQ for how to handle this. The
approach is not to put everything in the header file, but rather to
#include the .cpp (just once) at some point to avoid linker errors.
It's actually pretty nice in terms of compile times, under some
configurations.
Luke
gobis wrote: Hello everyone,
After I could not overload the << operator as a friend operator in my template class (yes, it did not have to be a template class, but I was testing something for the class I was going to teach) , I declared the operator outside the class definition. This would prevent the operator from accessing the private elements within the class, so I provided access to elements of the private vector array thru a public member function. But then I found that I could not place the const specifier before the templated class argument in the overloaded operator definition:
template <class C> ostream& operator << (ostream& os, const Polynom<C>& p) { for(int i=p.GetOrder()+ 1; i>0; i--) { os << p.Coeff(i) << "*x^" << i << " + "; } os << p.Coeff(0) << endl; return os; }
The compiler (Bloodshed Dev C++) complained that passing a Polynom<int> or a Polynom<double> instance to the operator would discard qualifiers. I suppose the compiler wants the array member returned by the Coeff(int) member function to be const as well, but I could not add the const specifier in that definition. It did not supress the error message.
Can anybody see what I am doing wrong? Relevant code follows:
in the .hpp file:
template <class C> class Polynom { /*** Constructors and Destructors ***/ ... /*** Public methods ***/ ... C Coeff(int i);
Redeclare the above member function as:
C Coeff(int i) const;
so that it can be called operator<<().
... /*** Data members ***/ private: vector<C> coef; };
in the .cpp file:
template <class C> C Polynom <C>::Coeff(in t i) { return coef[i]; }
Move this definition of Coeff() into the Polynom's header file, so that
it is visible to client code. Class template implementations generally
are implemented completely in a .h file and have no .cpp file at all.
Greg
gobis wrote: Hello everyone,
After I could not overload the << operator as a friend operator in my template class (yes, it did not have to be a template class, but I was testing something for the class I was going to teach) , I declared the operator outside the class definition. This would prevent the operator from accessing the private elements within the class, so I provided access to elements of the private vector array thru a public member function. But then I found that I could not place the const specifier before the templated class argument in the overloaded operator definition:
template <class C> ostream& operator << (ostream& os, const Polynom<C>& p) { for(int i=p.GetOrder()+ 1; i>0; i--) { os << p.Coeff(i) << "*x^" << i << " + "; } os << p.Coeff(0) << endl; return os; }
The compiler (Bloodshed Dev C++) complained that passing a Polynom<int> or a Polynom<double> instance to the operator would discard qualifiers. I suppose the compiler wants the array member returned by the Coeff(int) member function to be const as well, but I could not add the const specifier in that definition. It did not supress the error message.
Can anybody see what I am doing wrong? Relevant code follows:
in the .hpp file:
template <class C> class Polynom { /*** Constructors and Destructors ***/ ... /*** Public methods ***/ ... C Coeff(int i);
Redeclare the Coeff member function like so:
C Coeff(int i) const;
so that it can be called from within operator<<().
in the .cpp file: template <class C> C Polynom <C>::Coeff(in t i) { return coef[i]; }
Move this definition of Coeff() into the Polynom's header file, so that
it is visible to client code. Class template implementations generally
are implemented completely in a .h file and have no .cpp file at all.
Greg This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
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