fork download 
  1. #include <iostream>
  2.  
  3. template <typename T>
  4. class fast_arg
  5. {
  6. public:
  7.     fast_arg(const T & val)
  8.     : lval_(&val), rval_(nullptr) {}
  9.     fast_arg(T &&val)
  10.     : lval_(nullptr), rval_(&val) {}
  11.  
  12.     void copy_to(T &target)
  13.     {
  14.         if (lval_) target = *lval_;
  15.         else       target = std::move(*rval_);
  16.     }
  17.  
  18. private:
  19.     const T *lval_;
  20.     T *rval_;
  21. };
  22.  
  23. class logged_creation
  24. {
  25. public:
  26.     logged_creation() {std::cout << "def ctor\n";}
  27.     logged_creation(const logged_creation &) {std::cout << "copy ctor\n";}
  28.     logged_creation(logged_creation &&) {std::cout << "move ctor\n";}
  29.     logged_creation& operator = (const logged_creation &) {std::cout << "copy assignment\n";}
  30.     logged_creation& operator = (logged_creation &&) {std::cout << "move assignment\n";}
  31. };
  32.  
  33. template <typename T>
  34. class foo
  35. {
  36. public:
  37.     void func(fast_arg<T> val)
  38.     {
  39.         T v;
  40.         val.copy_to(v);
  41.     }
  42. };
  43.  
  44. int main()
  45. {
  46.     foo<logged_creation> f;
  47.     std::cout << "LValue:\n";
  48.     logged_creation i;
  49.     f.func(i);
  50.     std::cout << "RValue:\n";
  51.     f.func(logged_creation());
  52. }
  53.  
Success #stdin #stdout 0s 3296KB
comments (?)
stdin 
Standard input is empty
stdout 
LValue:
def ctor
def ctor
copy assignment
RValue:
def ctor
def ctor
move assignment
https://ideone.com/fTORB3
language:
C++14 (gcc 8.3)
created:
12 years 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!