向量和常量

2021-12-21 00:00:00 constants vector c++ stl

考虑一下

 void f(vector<const T*>& p)
 {
 }
 int main()
 { 
  vector<T*> nonConstVec;
  f(nonConstVec);
 }

以下不编译.问题是 vector 不能转换为 vector ，这似乎对我来说不合逻辑，因为存在从 T* 到 const T* 的隐式转换.这是为什么?

The following does not compile.The thing is that vector<T*> can not be converted to vector <const T*> , and that seems illogically to me , because there exists implicit conversion from T* to const T*. Why is this ?

vector 也不能转换为 vector ，但这是意料之中的，因为 const T* 不能隐式转换为 T*.

vector<const T*> can not be converted to vector <T*> too, but that is expected because const T* can not be converted implicitly to T*.

推荐答案

我在您的代码中添加了几行.这足以说明为什么不允许这样做:

I've added a few lines to your code. That's sufficient to make it clear why this is disallowed:

void f(vector<const T*>& p)
 {
    static const T ct;
    p.push_back(&ct); // adds a const T* to nonConstVec !
 }
 int main()
 { 
  vector<T*> nonConstVec;
  f(nonConstVec);
  nonConstVec.back()->nonConstFunction();
 }

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