当我使用 c++11 编译以下程序时，出现错误 error: cannot add a default template argument to the definition of a member of a class template。为什么编译器不允许您在成员函数定义中使用默认模板参数？

#include <iostream>

template<typename A, typename T = int>
class my_class
{
private:
  void dosomething();
};

template<typename A, typename T = int>
void my_class<A, T>::dosomething()
{

}

int main( ) 
{ 
  B<int> obj;

  return 0;
}

最佳答案

来自 [temp.param]/9 (粗体是我强调)

A default template-argument is a template-argument (17.3) specified after = in a template-parameter. A default template-argument may be specified for any kind of template-parameter (type, non-type, template) that is not a template parameter pack (17.5.3). A default template-argument may be specified in a template declaration. A default template-argument shall not be specified in the template-parameter-lists of the definition of a member of a class template that appears outside of the member’s class. A default template-argument shall not be specified in a friend class template declaration. If a friend function template declaration specifies a default template-argument, that declaration shall be a definition and shall be the only declaration of the function template in the translation unit.

关于c++ - 错误 : cannot add a default template argument to the definition of a member of a class template，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/60098826/