Re: template class, methods and friend, unable to link

suresh.amritapuri wrote:


Let's make it very simple to start.

------------------------------------------------ foo.h
template<class T> void foo(T t); // declaration
------------------------------------------------ foo.cpp
#include <foo.h>
#include <typeinfo>
#include <iostream>

template<class T> void foo(T t) // definition
{
    std::cout << "foo(" << typeid(T).name() << ")\n";
}

template void foo<int>(int); // explicit instantiation
template void foo<double>(int); // explicit instantiation
------------------------------------------------ main.cpp
#include <foo.h>

int main()
{
     foo(42); // OK
     foo(3.14159); // OK
     foo('a'); // will not link : foo<char> undefined
}
----------------------------------------------------------

Now, the code above is untested, but conveys the general idea of how
templates can be made "available" without including the definitions of
the functions into the header: the explicit instantiation mechanism.

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask