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  1. #include <iostream>
  2. #include <vector>
  3. #include <functional>
  4. #include <algorithm>
  5. #include <iterator>
  6. #include <sstream>
  7.  
  8. using namespace std;
  9.  
  10. struct BaseGoDeeper { 
  11.   virtual void operator()(int i) = 0;
  12.   ~BaseGoDeeper() {};
  13. };
  14.  
  15. struct A : BaseGoDeeper { 
  16.   void operator()(int /*i*/) { cout << "A" << endl; } 
  17. };
  18.  
  19. struct B : BaseGoDeeper { 
  20.   void operator()(int /*i*/) { cout << "B" << endl; } 
  21. };
  22.  
  23. struct SubAlgorithm {
  24.   BaseGoDeeper& a_;
  25.   SubAlgorithm (BaseGoDeeper& a) : a_(a) {}
  26.   void operator()(int i) { 
  27.     // do some stuff and then do
  28.     a_(i);
  29.   }
  30. };
  31.  
  32. template<typename SubAlgorithm, typename Collection>
  33. void Alrogirthm(SubAlgorithm& f, Collection& stuff) {
  34.   // In my code f is invoked ~ 1e9 times (it's a loop that is executed
  35.   // ~ 1e6 times, and stuff.size() is ~1000). The application spends ~90% of
  36.   // it's time in this function. But for the sake of example:
  37.   for_each(stuff.begin(), stuff.end(), f);
  38. }
  39.  
  40. BaseGoDeeper* CreateGoDeeper(bool runtime_flag) {
  41.   if (runtime_flag) {
  42.     return new A();
  43.   }
  44.   return new B();
  45. }
  46.  
  47. int main(int , char**) {
  48.   stringstream ss;
  49.   ss << true << " " << false;
  50.  
  51.   vector<int> stuff;
  52.   stuff.push_back(1);
  53.  
  54.   while (ss.good()) {
  55.     bool runtime_flag;
  56.     ss >> runtime_flag;
  57.  
  58.     BaseGoDeeper* go_deeper_algorithm = CreateGoDeeper(runtime_flag);
  59.     SubAlgorithm sub_algorithm(*go_deeper_algorithm);
  60.     Alrogirthm(sub_algorithm, stuff);
  61.     delete go_deeper_algorithm;
  62.   }
  63.   return 0;
  64. }
Success #stdin #stdout 0s 3032KB
comments (?)
stdin 
Standard input is empty
stdout 
A
B
https://ideone.com/YAYafr
language:
C++ (gcc 8.3)
created:
12 years ago
visibility:
public

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