这种部分模板特化有什么问题吗？

发布于 2024-10-09 07:25:10 字数 639 浏览 1 评论 0原文

template<typename Retval, typename Op, typename... Args>
Retval call_retval_wrapper(CallContext &callctx, Op const op, Args &...args);

template<typename Op, typename ...Args>
bool call_retval_wrapper<bool, Op, Args>(
        CallContext &callctx, Op const op, Args &...args) {
    (callctx.*op)(args...);
    return true;
}

稍后在代码中调用它：

call_retval_wrapper<bool>(callctx, op, args...)

给出以下错误：

src/cpfs/entry.cpp:1908：错误：函数模板部分专业化 'call_retval_wrapper' 不允许的

原文

template<typename Retval, typename Op, typename... Args>
Retval call_retval_wrapper(CallContext &callctx, Op const op, Args &...args);

template<typename Op, typename ...Args>
bool call_retval_wrapper<bool, Op, Args>(
        CallContext &callctx, Op const op, Args &...args) {
    (callctx.*op)(args...);
    return true;
}

Calling this later in the code:

call_retval_wrapper<bool>(callctx, op, args...)

Gives this error:

src/cpfs/entry.cpp:1908: error:
function template partial
specialization
‘call_retval_wrapper<bool, Op, Args>’
is not allowed

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‘画卷フ 2024-10-16 07:25:10

在 C++ 中，您不能对函数进行部分模板专门化，只能对结构和类进行部分模板专门化。因此，您应该要么进行完全专业化，要么使用具有静态成员函数的类（当然这与函数不同）

您可以使用一些使用类的技巧：

template<typename Retval, typename Op, typename... Args>
struct my_traits {
 static Retval call_retval_wrapper(CallContext &callctx, Op const op, Args &...args);
};

 template<typename Op, typename ...Args>
 struct my_traits<bool,Op,Args...> {
   static bool call_retval_wrapper<bool, Op, Args>(
    CallContext &callctx, Op const op, Args &...args) {
      (callctx.*op)(args...);
     return true;
   }
 };

template<typename Retval, typename Op, typename... Args>
Retval call_retval_wrapper(CallContext &callctx, Op const op, Args &...args)
{
     return my_traits<Retval,Op,Args...>::call_retval_wrapper(calllxtx,op,args...);
}

类似的东西

In C++ you can't do partial template specialization for functions, only for structures and classes. So you should either to do full specialization or use classes with static member functions (of course this is not same as functions)

You may use some tricks using classes:

template<typename Retval, typename Op, typename... Args>
struct my_traits {
 static Retval call_retval_wrapper(CallContext &callctx, Op const op, Args &...args);
};

 template<typename Op, typename ...Args>
 struct my_traits<bool,Op,Args...> {
   static bool call_retval_wrapper<bool, Op, Args>(
    CallContext &callctx, Op const op, Args &...args) {
      (callctx.*op)(args...);
     return true;
   }
 };

template<typename Retval, typename Op, typename... Args>
Retval call_retval_wrapper(CallContext &callctx, Op const op, Args &...args)
{
     return my_traits<Retval,Op,Args...>::call_retval_wrapper(calllxtx,op,args...);
}

Something like that

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七色彩虹 2024-10-16 07:25:10

您还需要在这一行中解压：

bool call_retval_wrapper<bool, Op, Args...>(

You need to unpack in this line too:

bool call_retval_wrapper<bool, Op, Args...>(

回复收藏 0 原文

后知后觉 2024-10-16 07:25:10

你可以尝试这样的事情（ideone）：

template<typename Retval, typename Op, typename... Args>
struct call{
  static Retval retval_wrapper(Op const op, Args &&...args);
};

template<typename Op, typename ...Args>
struct call<bool, Op, Args...>{
  static bool retval_wrapper(Op const op, Args &&...args){
    return true;
  }
};

int main(){
  call<bool, bool, bool>::retval_wrapper(true, true);
}

我没有阅读完整的C++0x规范，但现在可以部分特化函数吗？

You can try something like this (ideone) :

template<typename Retval, typename Op, typename... Args>
struct call{
  static Retval retval_wrapper(Op const op, Args &&...args);
};

template<typename Op, typename ...Args>
struct call<bool, Op, Args...>{
  static bool retval_wrapper(Op const op, Args &&...args){
    return true;
  }
};

int main(){
  call<bool, bool, bool>::retval_wrapper(true, true);
}

I didn't read the full C++0x spec, but is it possible to partial specialize function now?

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