[TriLUG] OT: A C++ Templated Class Problem

[Owen Berry]

On Fri, Apr 14, 2006 at 12:52:32PM -0400, Ed Hill wrote:
> On Fri, 2006-04-14 at 12:17 -0400, Owen Berry wrote:
> > I think you need to inline all your template functions. In other words,
> > all your code needs to be in the header file.
> 
> Yes, the most general way is to put all the code in the headers and this
> is exactly whats done with the STL since all the possible template types
> cannot be known until they get instantiated.  A lot of C++ can be
> all-headers and no-libs.
> 
> Another approach, one that you can use if you know that only a certain
> small number of types will always be used, is to compile libraries
> containing explicit instantiations.  In that strategy, the headers may
> be strictly declaratory such as:
> 
>   namespace foo {
>     template <class Real> class Bar {
>     public:
>         Bar();
>         ~Bar();
>         other_funcs();
>     private:
>         //  ...data...
>     };
>   }
> 
> and then separate files may contain the actual template code plus the
> necessary explicit instantiations such as:
> 
>   namespace foo {
>     template class Bar<float>;
>     template class Bar<double>;
>   }
> 
> which are then compiled to produce libraries.  I mention this explicit
> instantiation strategy since its commonly used for C++ where there is a
> lot of mathematical work being done and there are often only a few
> appropriate numerical types available.  Your "matrix" code might be a
> good fit.
> 
> Ed

Yes, good point Ed.

Owen