Re: [Dev-C++] Templates

[Michael P. <mdp...@ya...>]

Templates are more like Macros.  Glorified Macros but
macro like all the same.

When you create an instance of a template, the
compiler needs all of the information immediately to
create it.  It will not be able to leave it to the
linker like a regular class.  

This makes sense since the instance construction is
dependent upon the data types feed to the template.
Each template method construction is dependent upon
these data types.

--- Graeme Foster <gr...@dr...> wrote:
> I have created a template, as follows:
> 
> template <class T,long px=0, long py=0, long pz=0>
> class c3DMatrix
> {
>    private:        // Private member functions and
> variables
>    protected:        // Protected member functions
> and variables
>    public:        // Public member functions and
> variables
> };
> 
> template <class T,long px, long py, long pz>
> T c3DMatrix<T, px, py, pz>::get(long x, long y, long
> z)
> {
>    // some code to return the appropriate element
> }
> 
> When I include the declaration and source code in
> the C++ header file
> everything works correctly. However if I remove the
> source code out to a
> separate cpp file I get a linker error as follows:
> 
> undefined reference to
> 'c3DMatrix<int,5,2,4>::get(long,long,long)
> 
> source code is as follows...
> 
> #include "c3DMatrix.hpp"
> 
> template <class T,long px, long py, long pz>
> T c3DMatrix<T, px, py, pz>::get(long x, long y, long
> z)
> {
>    // some code to return the appropriate element
> }
> 
> All three files (header, source and driver file are
> include in the project)
> 
> Any advice greatly appreciated.
> 
> Graeme
> 
> 
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>
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