[LC++]Template functions and linking

[Mark Phillips]

Suppose you have some template function, declared in some header
file.

Eg, dosomething.h:

   template<typename A>
   int doit(A const& a);

Then you implement this function in another file, dosomething.cc:

   template<typename A>
   int doit(A const& a) {
     int it;
     // ... do something
     return it;
   }

Finally, you want to use this function in file main.cc:

   #include "dosomething.h"

   ...
   double x;
   cout<<doit(x)<<endl;
   ...

The problem is, that when g++ creates the object file dosomething.o,
it doesn't know what typenames it should use for creating versions
of doit.  When compiling main.cc, it wants a doit<double>, but
at linking, no such beast exists.

One solution would be to put the implementation of doit in the header
and make it inline.

Is there a better way?

Thanks,

Mark.

--
Dr Mark H Phillips
Research Analyst (Mathematician)

AUSTRICS - smarter scheduling solutions - www.austrics.com

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