部分模板专业化有什么问题? [英] What is wrong with partial template specialization?

问题描述

我正在编写一个带有一个类型参数和一个布尔值的模板化类，这是代码:

I am writing a templated class with one type paramenter and one boolean, here is the code:

template<class T, bool p = true>
class A
{
private:
    T* ptr;
public:
    A();
};


template<class T>
A<T,true>::A()
{
    ptr = 0xbaadf00d;
}

int main()
{
    A<int> obj;
    A<int, false> o;
    return(0);
}

我得到了这些编译错误:

And I am getting these compilation errors:

Error   1   error C3860: template argument list following class template name must list parameters in the order used in template parameter list tst.cpp 15
Error   2   error C2976: 'A<T,p>' : too few template arguments  tst.cpp 15

我做错了什么? 还是出于某种原因而被禁止部分专门化非类型参数?

What am I doing wrong? Or is it for some reason forbidden to specialize non-type parameters partially?

如果同时在if语句中使用boolean参数，则会收到以下警告:

At the same time if I use the boolean parameter in an if statement, I'm getting this warning:

Warning 1   warning C4127: conditional expression is constant

所以我应该专门做这类事情...

So I am supposed to do specializations for this kind of things...

任何帮助将不胜感激！ :)

Any help would be highly appreciated! :)

提前谢谢！！！！

推荐答案

您正在尝试部分地专门化方法.那是不允许的.您只能对整个班级进行部分专业化训练.专门化该类后，可以为部分专门化的类提供方法的非专门化定义.

You are trying to partially specialize a method. That is not allowed. You can only partially specialize the whole class. Once you have specialized the class, you can then provide a non-specialized definition of the methods for the partially specialized class.

以下是一些可能满足您要求的代码的示例:

Here is an example of some code that might do what you want:

template<class T, bool p = true>
class A
{
private:
    T* ptr;
public:
    A();
};

template <class T>
class A<T,true> {
private:
    T* ptr;
public:
    A();
};


template <class T>
class A<T,false> {
private:
    T* ptr;
public:
    A();
};

template<class T>
A<T,true>::A()
{
    ptr = reinterpret_cast<T *>(0xbaadf00d);
}

template<class T>
A<T,false>::A()
{
    ptr = 0;
}

int main()
{
    A<int> obj;
    A<int, false> o;
    return(0);
}

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