Re: [Dev-C++] templates + linker error

[Jorge G. <jor...@gm...>]

I try with this. and no problem

#include <iostream>
#include <cstdlib>
#include "mypair.hpp"
#include "mypair.cpp"   // i include the implementation in the source
principal.cpp

the question is less efficient?, or its ok?

bytes


2008/5/26, Per Westermark <pw...@ia...>:
>
> The compiler can't create the code for a template function unless it sees
> the implementation when you try to use the template function.
>
> You should have the implementation of your multiply function in the header
> file, and not hidden in a cpp file.
>
> It is only the linker that will see the generated code from multiple cpp
> files, and neither the compiler nor the compiler knows that calc.cpp
> should create a specific version of the multiply function with the double
> data type.
>
> /pwm
>
>
> On Sun, 25 May 2008, Jorge Guevara wrote:
>
> > i have 3 source  calc.h calc.cpp and principal.cpp (i compilated it with
> > devcpp)
> >
> > i have this error:
> > In function `main':
> > [Linker error] undefined reference to `calc<double>::multiply(double,
> > double)'
> > ld returned 1 exit status
> > [Build Error] ["Proyecto] Error 1
> >
> > somebody could help me please :)
> >
> > /********calc.h******/
> > #ifndef _CALC_H
> > #define _CALC_H
> >
> > template <class A_Type> class calc
> > {
> > public:
> > A_Type multiply(A_Type x, A_Type y);
> > A_Type add(A_Type x, A_Type y);
> >
> > };
> >
> > #endif
> >
> > /****calc.cpp******/
> > #include "calc.h"
> > #include <iostream>
> > using namespace std;
> >
> > template <class A_Type> A_Type calc<A_Type>::multiply(A_Type x,A_Type y)
> > {
> > return x*y;
> > }
> > template <class A_Type> A_Type calc<A_Type>::add(A_Type x, A_Type y)
> > {
> > return x+y;
> > }
> >
> >
> > /******principal.cpp*****/
> > #include "calc.h"
> > #include <iostream>
> > #include <cstdlib>
> >
> > using namespace std;
> >
> > int main()
> > {
> > calc <double> a_calc_class;
> > double a, b;
> > a=4.3;
> > b=3.4;
> > a_calc_class.multiply(a,b);
> >
> > system("PAUSE");
> > return EXIT_SUCCESS;
> > }
> > /***************************/
> >
>
>


-- 
Ing. Jorge Luis Guevara Diaz
Bs Ciencias de la Computacion
Maestrante en Ciencia de la Computación
http://jorge.sistemasyservidores.com   http://inf.unitru.edu.pe/~jlgd
Escuela de Informática - Universidad Nacional de Trujillo
Escuela de Ingeniería de Sistemas - Universidad Privada del Norte