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  1. #include <iostream>
  2. #include <vector>
  3. #include <algorithm>
  4.  
  5. class CompareMe
  6. {
  7.  public:
  8.     CompareMe(int in) : toCompare(in){}
  9.     int toCompare;
  10. };
  11.  
  12. class Comparitor
  13. {
  14. public:
  15.     bool operator()(CompareMe * first, CompareMe * second)
  16.     {
  17.         return first->toCompare < second->toCompare;
  18.     }
  19. };
  20.  
  21. class ComparitorOuter : public Comparitor{};
  22.  
  23. int main()
  24. {
  25.     class ComparitorInner : public Comparitor{};
  26.  
  27.     std::vector<CompareMe *> compares;
  28.     compares.push_back(new CompareMe(0));
  29.     compares.push_back(new CompareMe(1234));
  30.     compares.push_back(new CompareMe(163));
  31.     compares.push_back(new CompareMe(6));
  32.     compares.push_back(new CompareMe(12));
  33.  
  34.     //This works, and properly sorts the array
  35.     ComparitorOuter comparitor;
  36.     std::sort(compares.begin(), compares.end(), comparitor);
  37.  
  38.     //Uncomment out the sort below and it will not compile.
  39.     ComparitorInner comparitorInner;
  40.     std::sort(compares.begin(), compares.end(), comparitorInner);
  41.  
  42.     std::vector<CompareMe *>::iterator it;
  43.     for(it = compares.begin(); it != compares.end(); ++it)
  44.     {
  45.         std::cout << (*it)->toCompare << std::endl;
  46.     }
  47. }
Success #stdin #stdout 0s 3032KB
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stdin
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Standard input is empty
stdout
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0
6
12
163
1234
https://ideone.com/E5X5vM
language:
C++14 (gcc 8.3)
created:
13 years ago
visibility:
public

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