simple error woth templates

simple error woth templates

[Andre Kirchner]

Hi,

I have made this program to learn templates, but gcc
keeps says that there's an undefined reference to
`Dog<int,long>::Dog[in-charge](int,int,long,log)` at
the line marked
bellow.
Could someone show me what's wrong?

Thanks in advance,

Andre


**** Dog.h *****

#ifndef IOSTREAM
  #define IOSTREAM
  #include <iostream.h>
#endif
 
template < class CLASS_A, class CLASS_B >
class Dog
{
  public:
    Dog( CLASS_A firstNumber, CLASS_A secondNumber,
CLASS_B thirdNumber, CLASS_B forthNumber );
    ~Dog(){};   
    void showBigger();

  private:
    CLASS_A number_A;
    CLASS_B number_B;
};


*** Dog.cpp ***

#ifndef DOG
  #define DOG
  #include "Dog.h"
#endif

template < class CLASS_A, class CLASS_B >
Dog< CLASS_A, CLASS_B >::Dog( CLASS_A firstNumber,
CLASS_A secondNumber, CLASS_B thirdNumber, CLASS_B
forthNumber )
{
  number_A = ( firstNumber>secondNumber
)?firstNumber:secondNumber;
  number_B = ( thirdNumber>forthNumber
)?thirdNumber:forthNumber;
}  

template < class CLASS_A, class CLASS_B >
void Dog< CLASS_A, CLASS_B >::showBigger()
{
  cout << number_A << endl;
  cout << number_B << endl;
}


*** main.cpp ***

#ifndef DOG
  #define DOG
  #include "Dog.h"
#endif

int main( int argc, char *argv[] )
{
  Dog < int, long > theDog( 10, 20, 30l, 40l );
  
//  theDog.showBigger;

  return( 0 );
}

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Re: simple error woth templates

[Eljay Love-Jensen]

Hi Andre,

It appears that you neglected to #include "Dog.cpp" in your Main.cpp source 
file.

Personally, I'm not a proponent of naming a header file with a ".cpp" 
extension.  But that's just me.

HTH,
--Eljay

Re: simple error woth templates

[llewelly]

Andre Kirchner <supercroc1974@yahoo.com> writes:

> Hi,
> 
> I have made this program to learn templates, but gcc
> keeps says that there's an undefined reference to
> `Dog<int,long>::Dog[in-charge](int,int,long,log)` at
> the line marked
> bellow.
> Could someone show me what's wrong?
[snip]

gcc does not support seperate compilation for templates.
    You must #include the definition of each template in each
    translation unit which uses it.

RE: simple error woth templates

[Lev Assinovsky]

Hi!
All template related code (declarations and definitions) should be avaliable 
to the caller (main in your case) at compile time.
I put your code into one file and 
it works fine. 

----
Lev Assinovsky
Aelita Software Corporation 
(now is a part of Quest Software)
O&S InTrust Framework Division, Team Leader
ICQ# 165072909


> -----Original Message-----
> From: Andre Kirchner [mailto:supercroc1974@yahoo.com]
> Sent: Thursday, April 22, 2004 6:27 PM
> To: gcc-help@gcc.gnu.org
> Subject: simple error woth templates
> 
> 
> Hi,
> 
> I have made this program to learn templates, but gcc
> keeps says that there's an undefined reference to
> `Dog<int,long>::Dog[in-charge](int,int,long,log)` at
> the line marked
> bellow.
> Could someone show me what's wrong?
> 
> Thanks in advance,
> 
> Andre
> 
> 
> **** Dog.h *****
> 
> #ifndef IOSTREAM
>   #define IOSTREAM
>   #include <iostream.h>
> #endif
>  
> template < class CLASS_A, class CLASS_B >
> class Dog
> {
>   public:
>     Dog( CLASS_A firstNumber, CLASS_A secondNumber,
> CLASS_B thirdNumber, CLASS_B forthNumber );
>     ~Dog(){};   
>     void showBigger();
> 
>   private:
>     CLASS_A number_A;
>     CLASS_B number_B;
> };
> 
> 
> *** Dog.cpp ***
> 
> #ifndef DOG
>   #define DOG
>   #include "Dog.h"
> #endif
> 
> template < class CLASS_A, class CLASS_B >
> Dog< CLASS_A, CLASS_B >::Dog( CLASS_A firstNumber,
> CLASS_A secondNumber, CLASS_B thirdNumber, CLASS_B
> forthNumber )
> {
>   number_A = ( firstNumber>secondNumber
> )?firstNumber:secondNumber;
>   number_B = ( thirdNumber>forthNumber
> )?thirdNumber:forthNumber;
> }  
> 
> template < class CLASS_A, class CLASS_B >
> void Dog< CLASS_A, CLASS_B >::showBigger()
> {
>   cout << number_A << endl;
>   cout << number_B << endl;
> }
> 
> 
> *** main.cpp ***
> 
> #ifndef DOG
>   #define DOG
>   #include "Dog.h"
> #endif
> 
> int main( int argc, char *argv[] )
> {
>   Dog < int, long > theDog( 10, 20, 30l, 40l );
>   
> //  theDog.showBigger;
> 
>   return( 0 );
> }
> 
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