fork download
copy 
  1. #include <iostream>                
  2. #include <string>                  
  3. #include <boost/ref.hpp>                           
  4. #include <boost/variant.hpp>
  5.  
  6. template <typename T>
  7. class CopyOrRef 
  8. {
  9. private:
  10.     typedef const T CopyType;
  11.     typedef typename boost::reference_wrapper<const T> RefType;
  12. 	boost::variant<CopyType, RefType> _copyOrRef;
  13. public:
  14.     CopyOrRef(const T & value) : _copyOrRef(value) { std::cout << "ctor 1" << std::endl; } // stores copy
  15.     CopyOrRef(const T * ptr) : _copyOrRef(boost::ref(*ptr)) { std::cout << "ctor 2" << std::endl; } // stores reference
  16.     CopyOrRef(const boost::reference_wrapper<T> & r) : _copyOrRef(boost::cref(r.get())) { std::cout << "ctor 3" << std::endl; } // stores reference
  17.     CopyOrRef(const boost::reference_wrapper<const T> & r) : _copyOrRef(r) { std::cout << "ctor 4" << std::endl; } // stores reference
  18.  
  19.     const T & get()
  20.     { 
  21.     	return _copyOrRef.which() == 0 ?
  22.     		*(boost::get<CopyType>(&_copyOrRef)) :
  23.     		*(boost::get<RefType>(&_copyOrRef)); 
  24.     }
  25.  
  26.     bool isCopy() const { return _copyOrRef.which() == 0; } 
  27.     bool isRef() const { return _copyOrRef.which() == 1; } 
  28. };
  29.  
  30. class NonCopyConstructible
  31. {
  32. public:
  33. 	NonCopyConstructible() {}
  34. private:
  35. 	NonCopyConstructible(NonCopyConstructible & that);
  36. };
  37.  
  38. int main()
  39. {
  40.  
  41.     std::string s = "s";
  42. 	CopyOrRef<std::string> test1(s);
  43. 	CopyOrRef<std::string> test2("ss");
  44. 	CopyOrRef<std::string> test3(&s);
  45. 	CopyOrRef<std::string> test4(boost::ref(s));
  46. 	CopyOrRef<std::string> test5(boost::cref(s));
  47.  
  48.     std::cout << "test1: isCopy=" << test1.isCopy() << ", isRef=" << test1.isRef() << " : " << test1.get()  << std::endl;
  49.     std::cout << "test2: isCopy=" << test2.isCopy() << ", isRef=" << test2.isRef() << " : " << test2.get()  << std::endl;
  50.     std::cout << "test3: isCopy=" << test3.isCopy() << ", isRef=" << test3.isRef() << " : " << test3.get()  << std::endl;
  51.     std::cout << "test4: isCopy=" << test4.isCopy() << ", isRef=" << test4.isRef() << " : " << test4.get()  << std::endl;
  52.     std::cout << "test5: isCopy=" << test5.isCopy() << ", isRef=" << test5.isRef() << " : " << test5.get()  << std::endl;
  53.  
  54. 	NonCopyConstructible t;
  55. 	CopyOrRef<NonCopyConstructible> tt(boost::cref(t));
  56.  
  57. }
  58.  
Success #stdin #stdout 0.01s 5288KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
ctor 1
ctor 1
ctor 2
ctor 3
ctor 4
test1: isCopy=1, isRef=0 : s
test2: isCopy=1, isRef=0 : ss
test3: isCopy=0, isRef=1 : s
test4: isCopy=0, isRef=1 : s
test5: isCopy=0, isRef=1 : s
ctor 4
https://ideone.com/hyPb0a
language:
C++ 4.3.2 (gcc-4.3.2)
created:
1 day ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!