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  1. #include <iostream>
  2. #include <list>
  3. #include <algorithm>
  4. #include <iterator>
  5. using namespace std;
  6.  
  7.  
  8. class A {
  9. 	    int val; 
  10.     public:
  11.         A(int x=0) : val(x){}
  12.         A& operator= ( const A &rhs ) { return *this; }
  13.         void show() { cout<<val<<" ";}
  14.         int get() const { return val; }
  15. };
  16. class B: public A {
  17.     public:
  18.         B(int x=0) : A(x) {}
  19.         B( const B& rhs) : A(static_cast<A>(rhs)) {}
  20.         B(const A& rhs) : A(rhs) {}  // <================= WITHOUT THIS CTOR, IT FAILS TO COMPILE 
  21.         B& operator= ( const A &rhs ) { return *this; }
  22. };
  23.  
  24. int main() {
  25.     A a;
  26.     B b;
  27.     std::list < A > aa{ A(1), A(2), A(3)};
  28.     std::list < B > bb;
  29.     a = b; // works
  30.     b = a; // works
  31.     //std::copy(aa.begin(), aa.end(), bb.begin());  // ouch: to avoid
  32.     //for (auto &x : bb) x.show();  // ouch !! only copies on existing elements 
  33.     std::copy(aa.begin(), aa.end(), back_inserter<list<B>>(bb)); 
  34.     for (auto &x : bb) x.show(); cout<<endl; 
  35.     bb.assign(aa.begin(), aa.end());
  36.     for (auto &x : bb) x.show(); cout<<endl; 
  37.     std::copy(bb.begin(), bb.end(), back_inserter<list<A>>(aa)); 
  38.     std::copy(bb.begin(), bb.end(), aa.begin()); 
  39.  
  40.     std::list <int> xx; 
  41.     std::transform (aa.begin(), aa.end(), std::back_inserter<list<int>>(xx), [](const A&a){return a.get();});     
  42.     std::copy(xx.begin(), xx.end(), std::ostream_iterator<int>(cout,";")); cout<<endl; 
  43. 	return 0;
  44. }
Success #stdin #stdout 0s 3456KB
comments (?)
stdin
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Standard input is empty
stdout
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1 2 3 
1 2 3 
1;2;3;1;2;3;
https://ideone.com/n0rgVy
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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