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// -*- C++ -*-

// Copyright (C) 2005, 2006, 2009 Free Software Foundation, Inc.

//

// This file is part of the GNU ISO C++ Library.  This library is free

// software; you can redistribute it and/or modify it under the terms

// of the GNU General Public License as published by the Free Software

// Foundation; either version 3, or (at your option) any later

// version.

// This library is distributed in the hope that it will be useful, but

// WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

// General Public License for more details.

// You should have received a copy of the GNU General Public License

// along with this library; see the file COPYING3.  If not see

// <http://www.gnu.org/licenses/>.

// Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.

// Permission to use, copy, modify, sell, and distribute this software

// is hereby granted without fee, provided that the above copyright

// notice appears in all copies, and that both that copyright notice

// and this permission notice appear in supporting documentation. None

// of the above authors, nor IBM Haifa Research Laboratories, make any

// representation about the suitability of this software for any

// purpose. It is provided "as is" without express or implied

// warranty.

/**

 * @file hash_initial_size_example.cpp

 * An example of setting an initial size for a container object.

 */

/**

 * This example shows how to set the initial size of a hash-based

 * container object through its resize-policy object.

 */

#include <cassert>

#include <ext/pb_ds/assoc_container.hpp>

#include <ext/pb_ds/hash_policy.hpp>

using namespace std;

using namespace __gnu_pbds;

// A simple hash functor.

// hash could serve instead of this functor, but it is not yet

// standard everywhere.

struct int_hash : public unary_function<int, size_t>

{

  inline size_t

  operator()(const int& r_i) const

  { return r_i; }

};

int main()

{

  // Resize policy type.

  typedef

    hash_standard_resize_policy<

    // Size-policy type.

    hash_exponential_size_policy<>,

    // Trigger-policy type.

    hash_load_check_resize_trigger<>,

    /* Allow external access to size.

     *     This is just used in this example for using the

     *     get_actual_size method (which won't be accessible without

     *     this flag.

     */

    true>

    resize_policy_t;

  // A collision-probing hash table mapping ints to chars.

  typedef

    gp_hash_table<

    int,

    char,

    int_hash,

    equal_to<

    int>,

    // Combining function.

    direct_mask_range_hashing<>,

    // Probe function.

    linear_probe_fn<>,

    // Resize policy.

    resize_policy_t>

    map_t;

  // A resize-policy object with suggested initial size 256.

  resize_policy_t res(hash_exponential_size_policy<>(256));

  map_t g(int_hash(),

          equal_to<int>(),

          direct_mask_range_hashing<>(),

          linear_probe_fn<>(),

          res);

  // Check the actual size of the container object. In this case, this

  // should be the initial size given by the size policy object.

  assert(g.get_actual_size() == 256);

  // The logical size of g, though is 0 (it does not contain any elements).

  assert(g.size() == 0);

  return 0;

}