No deduction in a class template

2018-06-17 02:48:57

template<typename T> 
class A { 
  public: 
    A(T b) : a(b) { 
    } 
  private: 
    T a; 
}; 

A object(12); //Why does it give an error?

为什么不能自动从参数12推导出类型T？

Template argument deduction applies only to function and member function templates but not to class templates. So your code is ill-formed.

You need to provide the template argument explicitly.

A<int> object(12); //fine

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