c++stlvectorconstants

vector and const

Consider this

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

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

Solution

  • 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();
 }