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c++templates
Simon Ninon
Simon Ninon

Reputation: 2441

Template Specialization for member functions

I've recently discovered template specialization in C++.

template <typename T>
void    fct(void) {}

template <>
void    fct<int>(void) {}

int main(void) {
  fct<int>();
  return 0;
}

I'd like to use template specialization for member functions inside a class.

class   MyClass {
  public:
    template <typename T>
    static void fct(void) {}

    template <>
    static void   fct<int>(void) {}
};

int     main(void) {
  MyClass::fct<int>();

  return 0;
}

Unfortunately, compiling with g++ gives me the following error:

error: explicit specialization in non-namespace scope ‘struct MyClass’
error: template-id ‘toto<int>’ in declaration of primary template

I've noticed that doing template specialization works in main scope or in a namespace but not in a struct or in a class.

I've found something on stackoverflow about using a namespace like in the following code:

namespace myNameSpace {
  template <typename T>
  void fct(void) {}

  template <>
  void fct<int>(void) {}
}

class   MyClass {
  public:
    template <typename T>
    static void fct(void) {
      myNameSpace::fct<T>();
    }
};

int     main(void) {
  MyClass::fct<int>();

  return 0;
}

What am I doing wrong? Is it possible to make template specialization with member functions? If not, what is the best way to get around this? Is there a better way than using namespace to get around this?

Upvotes: 3

Views: 303

Answers (1)

Kerrek SB
Kerrek SB

Reputation: 476940

Write the specialization after the class definition:

class MyClass
{
public:
    template <typename T>
    static void fct(void) {}
};

template <>
void MyClass::fct<int>() {}

Upvotes: 5

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