unique_ptr with pool

#include <iostream>

#include "etl/memory.h"
#include "etl/pool.h"

// The object stored in the pool
struct S
{
  S(int a_, double b_)
    : a(a_), b(b_) 
  {
  }

  int    a;
  double b;
};

int main()
{
  // The pool to allocate from.
  etl::pool<S, 10> pool;

  // The deleter called by unique_ptr.
  auto pool_deleter = [&pool](auto ptr) 
    { 
      std::cout << "Releasing S(" << ptr->a << ", " << ptr->b << ") back to pool." << std::endl; 
      pool.destroy(ptr); 
    };

  using Unique = etl::unique_ptr<S, decltype(pool_deleter)>;

  Unique us1(pool.create(1, 2), pool_deleter);
  std::cout << "Created S(" << us1->a << ", " << us1->b << ") from pool." << std::endl;

  {
    // Unique with local scope.
    Unique us2(pool.create(3, 4), pool_deleter);
    std::cout << "Created S(" << us2->a << ", " << us2->b << ") from pool." << std::endl;
  }

  Unique us3(pool.create(5, 6), pool_deleter);
  std::cout << "Created S(" << us3->a << ", " << us3->b << ") from pool." << std::endl;
}