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Function templates and namespaces

Ok, I have 3 files: compare.h, compare.cpp, and main.cpp
I am trying to write a function template to compare two numbers and return the largest. I want to put the template prototype in compare.h, template definition in compare.cpp, and the code in main.cpp
My book explains how to do it with functions, but not with function templates. K, here is the code as I wrote it.

compare.h
=======

namespace compare
{
    template<class T> T max(const T num1, const T num2);
}

compare.cpp
========

#include "compare.h"

template<class T> T compare::max(const T num1, const T num2)
{
    return (num1 > num2 ? num1 : num2);
}


main.cpp
======

#include <iostream>
#include "compare.h"

using compare::max;

int main()
{
    std::cout << max(5.0, 7.0);

    return 0;
}



==========================
I recieve "unresolved externals .." when trying to compile. Also, in by book, it says "Because we are using class templates you will need to prefix each of the template definitions with keyword 'export'.  The code will the be fully compatible with ANSI/ISO standard .."
Question is, where exactly do I put this 'export' keyword?

Thanks.
0
krupini
Asked:
krupini
1 Solution
 
rstaveleyCommented:
Per the standard, you should implement the function as....

export template<class T> T compare::max(const T num1, const T num2)
{
    return (num1 > num2 ? num1 : num2);
}

...in compare.cpp.

However, I recommend that you put...

template<class T> T compare::max(const T num1, const T num2)
{
    return (num1 > num2 ? num1 : num2);
}

...into your header and lose the compare.cpp file, because not many compilers support the export keyword.
0
 
DexstarCommented:
@krupini:

>  I want to put the template prototype in compare.h, template definition in
> compare.cpp, and the code in main.cpp

For templates, you don't put the code in a .CPP file.  The linker has trouble finding it that way.  Just put the prototype and the main code in the header file (or don't have a prototype, just stick it in your header and be done with it!).

Hope That Helps,
Dex*
0
 
krupiniAuthor Commented:
Ah, very true. I have Visual Studio 2003 and Dev-Cpp (using GCC 3.2) and none of them support the 'export' keyword. Thanks!
0

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