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Mar 22nd, 2009
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Move template functions to a .cpp file

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According to this:
http://www.parashift.com/c++-faq-lit...html#faq-35.13

One way to keep only the function declaration in the .h file is to do this
C++ Syntax (Toggle Plain Text)
  1. ////////// file: Tools.h
  2. #include <iostream>
  3. #include <vector>
  4.  
  5. using namespace std;
  6.  
  7. template <typename T> T Sum(vector<T> &V);


C++ Syntax (Toggle Plain Text)
  1. ///////// file: Tools.cpp
  2. #include "Tools.h"
  3.  
  4. #include <iostream>
  5. #include <vector>
  6.  
  7. using namespace std;
  8.  
  9. template <typename T>
  10. T Sum(vector<T> &V)
  11. {
  12. 	T sum = static_cast<T>(0.0);
  13. 	for(unsigned int i = 0; i < V.size(); i++)
  14. 		sum += V[i];
  15.  
  16. 	return sum;
  17.  
  18. }
  19.  
  20. //this is the key line to tell the compiler to actually make this function for unsigned int
  21. template unsigned int Sum<unsigned int>(vector<unsigned int> &V);

However, what if you want this function for a type that Tools does not know about? ie
C++ Syntax (Toggle Plain Text)
  1. template Point Sum<Point>(vector<Point> &V);
will not work because Point has not been defined. If you make Tools depend on Point, but Point already depends on Tools, then there is a circular problem.

Any suggestions?

Thanks,
Dave
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Mar 22nd, 2009
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Re: Move template functions to a .cpp file

I'm not sure I understand your question. Why can't you just #include "Point.h" ? I do not see anything circular here.
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Re: Move template functions to a .cpp file

C++ Syntax (Toggle Plain Text)
  1. ////// file: Point.h
  2. #include "Tools.h"
  3. class Point
  4. {
  5. public: 
  6. double x,y,z;
  7. void OutputSum()
  8. {
  9. // do something using a function from Tools here
  10. }
  11. };

Then if I include Point in Tools is that not a problem?
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Mar 22nd, 2009
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Re: Move template functions to a .cpp file

> Then if I include Point in Tools is that not a problem?

I don't think it's a problem. Have you tried it? If so, and if it doesn't work, then post the entire code.
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Re: Move template functions to a .cpp file

It does work - but I didn't really want to do that anyway lol, so let me rephrase - is there any way to do this that doesn't involve having to add those two lines (the declaration with specific type and the include) to the .cpp? I've seen people use .txx files - is this what those are for?
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Re: Move template functions to a .cpp file

I don't know anything about .txx files.
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Mar 23rd, 2009
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Re: Move template functions to a .cpp file

.TXX: DataPerfect Text Storage (A file format to store ASCII-only characters)

Are your sure it was '.TXX' and not '.CXX'?
'.CXX' is a valid C++ extension ...
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Mar 23rd, 2009
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Re: Move template functions to a .cpp file

yup, its txx.
see section C.5 in this document:
http://public.kitware.com/vxl/doc/de...15.html#SEC158
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Re: Move template functions to a .cpp file

Click to Expand / Collapse  Quote originally posted by daviddoria ...
yup, its txx.
see section C.5 in this document:
http://public.kitware.com/vxl/doc/de...15.html#SEC158
I've seen .txx, or variants thereof, it is for compiled template files. Usually the contents of these are various things that need to be compiled to use a given template library, such as type-specific implementations of parts of the library, etc.

Thanx...
Sean
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Mar 24th, 2009
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Re: Move template functions to a .cpp file

Just build it like you would build a class library ...
Note: Creating a C++ library depends from compiler to compiler ...
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