c++ allocator

#include 
#include 
#include 
#include 


// g++ allocator_traits_test.cpp -std=c++11 -fPIC -Ofast -D_GLIBCXX_USE_CXX11_ABI=0 -o allocator_traits_test

template 
struct custom_allocator {
  typedef T value_type;
  custom_allocator() noexcept {}
  template  custom_allocator (const custom_allocator&) noexcept {}
  T* allocate (std::size_t n) { return static_cast(::operator new(n*sizeof(T))); }
  void deallocate (T* p, std::size_t n) { ::operator delete(p); }
};

typedef std::allocator_traits>::rebind_alloc other_allcator;

template 
constexpr bool operator== (const custom_allocator&, const custom_allocator&) noexcept
{return true;}

template 
constexpr bool operator!= (const custom_allocator&, const custom_allocator&) noexcept
{return false;}

int main () {
  std::vector foo = {10,20,30};
  for (auto x: foo) std::cout << x << " ";
  std::cout << 'n';
  return 0;
}