Why doesn't my program work when I try to partially specialize a function template?

Question

I am an beginner in template metaprogramming trying to implement generation of multiple versions of similar but slightly different code:

#include <iostream>

enum Type
{
   a1,
   a2
};
enum Style
{
   b1,
   b2
 };

 template<Type,Style> 
 void doSomething();
 {
   std::cout<<" some rubbish\n";
 };

Full specialization works well:

template<> 
void doSomething<a1,b2>()
{
   std::cout<<" this is my template parameters one :" <<a1<< " and  two:"<<b2<<std::endl;
 }

int main(int argc, char* argv[])
{
  doSomething<a1,b1>();
  doSomething<a1,b2>();

   return 0;
}

:some rubbish

:this is my template parameters one :0 and two:1

But partial specialization like below fails:

 template<Style Some> 
  void doSomething<a1,Some>()
 {
  // here I want to use sub-template on some: e.g do_other<Some>
 }

with error: error C2768: 'DoSomething' : illegal use of explicit template arguments

(Body of generic template is commented in this case, though it does not make any difference)

Such specialization is in all samples for partial specialization, but does not work for me. This confuses me a lot.

Very appreciative for any suggestions

The truth is you can't do partial specialization of function templates. See this other question: [Can I use partial template specialization for a (non-member) function?](http://stackoverflow.com/questions/1961659/can-i-use-partial-template-specialization-for-a-non-member-function) — R. Martinho Fernandes, Dec 02 '11 at 13:44

score 2 · Answer 1 · answered Dec 02 '11 at 13:42

2

In C++ you cannot do partial specialization for functions. Consider moving your functions to a class.

answered Dec 02 '11 at 13:42

parapura rajkumar

24,045
1
55
85

In real word these are indeed the methods of the class. Class is not templated though. Will have a look – user1077392 Dec 02 '11 at 13:53
1

If you omit a critical piece of information like that , you can only get partial answers – parapura rajkumar Dec 02 '11 at 13:58
Yep, seen the reference with detailed explanation. Thank you very much. – user1077392 Dec 02 '11 at 14:02

score 0 · Answer 2 · answered Dec 02 '11 at 13:46

0

C++ Priorities functions that uses specialization for your types, rest is handled by normal template function.

answered Dec 02 '11 at 13:46

nikola-miljkovic

652
4
14

Why doesn't my program work when I try to partially specialize a function template?

2 Answers2