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  1. #include <memory>
  2. #include <iostream>
  3.  
  4.  
  5. namespace wyf {
  6.  
  7.     // a stub to get things compiled
  8.     template <class>
  9.         struct EmptyBaseOptimizationHelper
  10.         {
  11.             int capacity_;
  12.             template <class X, class Y> EmptyBaseOptimizationHelper(X, Y) {}
  13.         };
  14.  
  15.     template<typename Tp, typename Allocator = std::allocator<Tp>>
  16.         class vector {
  17.           public:
  18.             // linker error occurs when calling this ctor with certain arguments
  19.             vector(std::size_t n, const Tp& val, const Allocator& alloc = Allocator());
  20.             // omitting other member functions.
  21.           private: // three data members to hold the objects and raw memory
  22.             Tp* begin_; // using pointer = value_type*;
  23.             Tp* end_;
  24.             using allocator_type =Allocator;
  25.             // Empty Base Optimization Helper class to hold both Allocator and capacity_
  26.             EmptyBaseOptimizationHelper<allocator_type> capacity_;
  27.         };
  28.     // still in vector.hpp, the implemention goes below
  29.     template<typename Tp, typename Allocator>
  30.         vector<Tp, Allocator>::vector(std::size_t n, const Tp& val, const Allocator& alloc) :
  31.             begin_(nullptr), end_(nullptr), capacity_(nullptr, alloc) {
  32.             }
  33. }
  34.  
  35. int main() {
  36.   wyf::vector<int> v2(10, 20);
  37.   std::cout << "It works";
  38. }
  39.  
Success #stdin #stdout 0s 3456KB
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Standard input is empty
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It works
https://ideone.com/rkhQqI
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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