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  1. // kjellkod playing with temporary objects. 
  2. // From Herb's Gotw: http://h...content-available-to-author-only...r.com/2013/05/09/gotw-2-temporary-objects-510/
  3. //
  4. // Cheers
  5. // KjellKod (.wordpress.com)
  6.  
  7. #include <iterator>
  8. #include <list>
  9. #include <string>
  10. #include <iostream>
  11.  
  12. using namespace std;
  13.  
  14. // no explicit keyword makes the implicit conversion possible. which can be avoided of course
  15. // with explicit employee(string str) ...
  16. struct employee {
  17.    string addr;
  18.  
  19.   employee(std::string str) : addr{str}{} // oops no explicit
  20.   bool operator==(const employee& other) const { return (addr.compare(other.addr) == 0); }
  21. };
  22.  
  23.  
  24.  
  25. // using unnecessary copies. Possible scenario if employee is created as above
  26. // 1) i++   (probably close to zero overhead?)
  27. // 2) == operator  implicit conversion from string to employee
  28. // 3) return value can be written {""}
  29. // 4) const reference to the arguments 
  30. // 5) why not just use for(auto& employee : emps) instead of for(begin, !=end, ++) to avoid temp iterators
  31. //
  32. string find_addr( list<employee> emps, string name ) {  // 4 
  33.     for( auto i = begin(emps); i != end(emps); i++ ) {  // 1, 5
  34.         if( *i == name ) {                              // 2
  35.             return i->addr;
  36.         }
  37.     }
  38.     return "";                                          // 3
  39. }
  40.  
  41.  
  42. string find_addr_improved( const list<employee>& emps, const string& name ) { 
  43.       for(auto& employee : emps) {  
  44.         if ( employee.addr == name)     return employee.addr;
  45.     }
  46.     return {""};   
  47. }
  48.  
  49. int main() {
  50.     auto colleagues = list<employee>{{"Kjell"}, {"Jeanine"}, {"Nathaniel"}, {"John"}}; 
  51.  
  52.     cout << find_addr(colleagues, {"Jeanine"}) << endl;
  53.     cout << find_addr_improved(colleagues, {"Kjell"}) << endl;
  54.  
  55.     return 0;
  56.  
  57. }
Success #stdin #stdout 0s 3032KB
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Jeanine
Kjell
https://ideone.com/d54ARz
Gotw #2 http://h...content-available-to-author-only...r.com/2013/05/09/gotw-2-temporary-objects-510/
Temporary variable instantiation
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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